Dust-jacket illustration of the first UK edition
|Cover artist||Thomas Derrick|
|Publisher||William Collins & Sons|
|27 January 1927|
|Media type||Print (hardback & paperback)|
|Pages||282 (first edition, hardback)|
|Preceded by||The Murder of Roger Ackroyd|
|Followed by||The Mystery of the Blue Train|
The Big Four is a work of detective fiction by Agatha Christie, first published in the UK by William Collins & Sons on 27 January 1927 and in the US by Dodd, Mead and Company later in the same year. It features Hercule Poirot, Arthur Hastings, and Inspector Japp. The UK edition retailed at seven shillings and sixpence (7/6) and the US edition at $2.00.
The structure of the novel is different from other Poirot stories, as it began from twelve short stories (eleven in the US) that had been separately published. This is a tale of international intrigue and espionage, therefore opening up the possibility of more spy fiction from Christie.:24
The opening chapters are set in Hercule Poirot's apartment in London. There is an abortive railway trip to Southampton and the return trip to London. There is then a visit to an unnamed village in Devon, situated in the vicinity of Dartmoor. The village of Chobham which Poirot visits next is an actual location in Surrey.:43–47 The action then moves to France, in the Passy area of Paris, and then back to the United Kingdom in the fictional location of Hatton Chase, seat of the Duke of Loamshire, followed by a visit to Market Hanford, Worcestershire. The narrative then returns to London and to London's Chinatown. There is also a visit to a restaurant in Soho, and then abroad to Belgium. There are two trips on ocean-going ships. Finally there is a railway trip from London to Paris and from there to South Tyrol in Italy.
Captain Arthur Hastings returns to England after an 18-month-long stay in Argentina. He intends to visit his old friend Hercule Poirot and is shocked to find Poirot about to leave for South America. Poirot wants to go to Rio de Janeiro where his newest client Abe Ryland awaits. The imminent departure of Poirot has to be postponed, however. An unexpected visitor called Mayerling comes in through Poirot's bedroom. There is no clue of how the man entered the upper floor apartment. Perhaps through the bedroom's window which is, however, at some distance from the ground. The man is covered from head to toes with dust and mud. He is emaciated as though he has been long imprisoned and with little access to food. He collapses on the floor. The only clue to what he wants is his saying Poirot's name (his only words) and writing the number 4, many times.
When Hastings mentions the Big Four, the man begins speaking about an international crime cartel of that name. He knows little of the four leaders, and tells them that Number 1 is a Chinese political mastermind named Li Chang Yen. He represents the brains of the Big Four. Number 2 is usually not named but is represented by a '$' or two stripes and a star, so he is probably American and he represents wealth. Number 3 is a Frenchwoman, and Number 4 is "the Destroyer" and otherwise unknown.
Poirot and Hastings summon a doctor who examines the patient and prescribes rest. Poirot and Hastings leave the man in the care of Poirot's housekeeper and set off to catch a train to Southampton. During the journey, Poirot suspects his South American mission was an excuse to get him out of the way. Deciding there is a case waiting for him in England, Poirot aborts his trip. He and Hastings take advantage of a stop in open terrain to exit the train. They return to London by car, only to find their visitor dead.
A doctor is summoned. An uninvited man arrives, claiming to work for a lunatic asylum and to be in search of an escaped inmate. He identifies the dead man as the escapee in question, then departs. Poirot calls the asylum and learns that there have been no recent escapes. Japp soon enters and recognises the dead man as Mayerling, a prominent figure in the Secret Service who had disappeared five years before. Poirot asks Hastings if he opened the windows, to which Hastings replies in the negative. Poirot examines the man and announces that Mayerling was gagged and poisoned by inhaling "prussic acid" (hydrogen cyanide). The hands of the lounge clock have been turned to 4 o'clock, and Poirot realises that the murderer was the man from the asylum. He was the Destroyer.
Poirot and Hastings visit John Ingles, a wealthy man, to ask him about Li Chang Yen and the Big Four. He saw a note from a fisherman who asked him for a few hundred pounds to hide himself from the Big Four. He has also heard stories of four men who opposed Li Chang Yen, and who were murdered by stabbing, poisoning, electrocution and cholera; and he has heard a similar story of a chemist who was burned to death in his residence. The note came from Hoppaton, so Poirot, Hastings and Ingles go to Hoppaton and discover that the man who wrote the note, a Mr Jonathan Whalley, has been murdered.
There are two suspects: his maid, Betsy, and his manservant, Grant. Whalley was hit on the head and then his throat was cut; and some jade figures of his have been stolen. Grant is the main suspect as his bloody footprints are found around the room, the jade figures were in his room, and there is blood on his room's doorknob. Grant is also under suspicion because he has been imprisoned before: he obtained this job through a prisoner help society.
Poirot finds a frozen leg of mutton which interests him very much. Poirot hypothesizes that the murderer was a young man who came in a trap, killed Whalley, and went away. His clothing was slightly bloodstained. Poirot talks to Grant and asks him whether he entered the room twice to take the jade figures. When he replies in the negative, Poirot reveals that no one noticed the murderer because he came in a butcher's cart. Mutton is not delivered on Sundays and if it had been delivered on Saturday it would not have been frozen. The man who gave Grant this job, Poirot assumes, was Number 4.
Poirot introduces Hastings to Captain Kent, who tells them of the sinking of many US boats after the Japanese earthquake. In the aftermath many crooks were rounded up, who referred to the Big Four. The latter have produced a form of wireless energy capable of focusing a beam of great intensity on any spot. A British scientist called Halliday was near success on this same concept when he was kidnapped on a visit to France. Halliday's wife tells Poirot that her husband went to Paris to talk to some people connected with his work. Among them was the notable French scientist Madame Olivier. Halliday had visited Madame Olivier; he had left her at six o'clock, dined alone at some restaurant, and gone back to his hotel. He walked out next morning and has not been seen since.
Poirot goes to Paris with Hastings. Poirot and Hastings visit Madame Olivier and question her. Upon leaving, they catch a glimpse of a veiled lady. A tree falls down, missing them. Poirot then explains to Hastings how Halliday was kidnapped: he was walking away when a lady caught up with him and told him Madame Olivier wanted to talk to him again. She led him into a narrow alley and then into a garden, telling him that Madame Olivier's villa was on the right-hand side. Then and there, Halliday was kidnapped. At the villa, Poirot asks to speak to the woman who just came in. She is the Countess Vera Rossakoff. When confronted with Poirot's theory, she phones the kidnappers to send Halliday back to the hotel. When Halliday returns he is too scared to speak. Then a man in a cloak, one of the Big Four, tries to persuade Poirot to stop his investigation. Hastings gets into a small fight with the stranger who then evades Poirot, Hastings, and the hotel manager with a clever disguise.
Madame Olivier tells Poirot that two men broke into her laboratory and attempted to steal her supply of radium. Poirot and Hastings board a train, and in the confusion of a signal failure caused by Poirot's friend, they return to Madame Olivier's villa to find the thieves. They are ambushed by thugs, and Olivier reveals herself to be Number 3. She says the two shall die by her hands to prevent their further interference. However, Poirot tells her that his cigarette contains a poisonous dart, and Olivier unties Hastings, who unties Poirot and binds and gags Olivier.
The two receive a letter from Abe Ryland who is annoyed at Poirot for refusing his offer. Poirot tells Hastings that Abe Ryland is Number 2, an American millionaire. Ryland soon releases news that he is looking for an efficient secretary, and Hastings gets the job, posing as a Captain Neville. He becomes suspicious of the manservant Deaves, and he learns that Ryland received an encoded letter telling him to go to a quarry at eleven o'clock. Hastings spies on Ryland, but is captured by Ryland and Deaves, who wait for Poirot. When he arrives he ambushes Ryland and Deaves with the help of ten Scotland Yard officers. Ryland is released after his manservant informs the police that all of it was just a wager, and Poirot realises that the manservant was Number Four.
A month later, they leave London to investigate the death of a Mr Paynter in Worcestershire. He has six Chinese servants, as well as his bodyguard Ah Ling, in whom Poirot is interested. When Paynter fell ill after a meal, Doctor Quentin was called; he told Paynter's nephew, Gerald, that he had given Paynter a hypodermic injection, and proceeded to ask strange questions about the servants. Paynter was found dead the next morning in a room locked from the inside. It seemed that he had fallen off his chair and into the gas fire, and the Doctor was blamed for leaving him in such a position.
Before his death, Paynter had written in ink "yellow jasmine" on his newspaper (yellow jasmine is a plant growing all over the house). Paynter had also drawn two lines at right angles under these words – a sign similar to the beginning of the number 4. At the inquest, Quentin comes under suspicion: he was not Paynter's regular doctor, and his recall of events is questioned. According to him, as soon as the door was shut Paynter told him that he was not feeling ill at all, but that the taste of his curry was strange.
It was claimed that Quentin injected him with strychnine rather than a narcotic. The curry was analysed, showing that it contained a deadly amount of opium, implicating the bodyguard Ah Ling, who had prepared it. Inspector Japp tells Poirot and Hastings that the key was found near the broken door and that the window was unlatched. Japp believes that the victim's face was charred to cover up the identity of the dead man, but Poirot believes the man to be Paynter. Poirot reveals that Doctor Quentin was Number 4, who entered the house and gave Paynter an injection of yellow jasmine rather than strychnine. He locked the door and exited through the window, returning later to put opium in the curry sample, throw Paynter into the fire, and steal a manuscript – the reason for the murder.
A month later, Japp informs Poirot of another mysterious death—that of chess grandmaster Gilmour Wilson, who collapsed and died from heart failure while participating in a match with another player, Doctor Savaronoff. Japp suspects he was poisoned and that the poison was intended for Savaronoff, a former Revolutionist in Russia who escaped from the Bolsheviks and was believed to have died during the revolution until his arrival in England. He previously refused several times to play a game of chess with Wilson, but eventually gave in. The match took place in Savaronoff's flat, with at least a dozen people watching the game.
There were no marks on Wilson's body except a small burn mark on his left hand, in which he was clutching a white bishop when he died, part of Savaronoff's set. As Poirot and Hastings enter the Doctor's flat, Poirot notices that the antique Persian rug has had a nail driven through it. After the proceedings in the flat, Poirot and Hastings return home and Poirot takes out a second white bishop. He weighed the one he took with the one Wilson was holding and discovered that the one he was holding was heavier. He explains that the bishop has a metal rod inside it, so that the current passing through the recently refurbished flat below is powered through the nail, into the also tampered-with table and into the bishop. The bishop was chosen because of Wilson's predictable first few moves (Wilson was electrocuted after playing the Ruy Lopez as White, consisting of the moves 1.e4 e5 2.Nf3 Nc6 3.Bb5 (see algebraic chess notation) – the square b5 was electrified and the white bishop with the metal rod was the light-squared one).
Poirot suspects the servant of the flat and Savaronoff's niece are working for the Big Four, believing the niece to be an imposter, as she hadn't been seen by her uncle prior to living with him in England since she was a small child. When Poirot and Hastings arrive at the flat to investigate further, however, Savaronoff's niece is gagged and unconscious, and Ivan and the Doctor are nowhere to be seen. Poirot deduces that Savaronoff did die in Russia and that Number Four impersonated him as a cover. He had avoided the match repeatedly, knowing that his inability to play chess would expose him as an imposter, as the real Doctor Savaronoff was the second best chess player in the world. When his refusals finally failed and he was forced to play Wilson, he arranged to have Wilson die before any chess strategy would be necessary on his part. With Number Four gone, the two are back to square one again.
Hastings in peril
Soon afterwards, Hastings receives a telegram from his manager indicating that his wife has been kidnapped in Argentina by the Big Four, and that if he wants to ensure her safety he must follow a Chinese servant and provide no notes for Poirot, who was out at the time. He leaves four books on the table as a message for Poirot, and follows the servant to an abandoned house in Chinatown, where he is taken to an Arabian-like room and forced to write to Poirot, asking for his help, by a servant of Li Chang Yen. Poirot is soon seen across the street and Hastings is forced to beckon him into the house. As he enters, however, Poirot throws a drugged smoke bomb into the house, knocking everyone unconscious, and Hastings is saved. Hastings is greeted by Poirot with the news that his wife has been safe for over three months in a place Poirot organized, having expected the Big Four to go after her, and that the telegram was faked to ensure his cooperation.
The identity of Number 4
Poirot's agents return from their work of identifying Number 4 and produce four names. A Mr Claud Darrell looks suspicious as he has visited both China and America. Very soon, Darrell's friend, Florence Monro, calls Poirot for information about Darrell. She mentions one important point, that when he eats he always picks up a piece of bread and dabs up the crumbs with it. She promises to send him a photo of Darrell. Twenty minutes later Miss Monro is hit by a car and killed, and Number Four has stolen the photograph.
Poirot, Hastings and Ingles meet with the Home Secretary and his client. Ingles leaves for China, and Poirot reveals an odd fact – he has a twin brother. The two arrive home to a nurse who says that her employer, Mr Templeton, often has gastric attacks after eating. When a sample of soup is tested and found to contain antimony, they set off again. The arrival of Templeton's adopted son causes a disturbance; he tells Poirot that he thinks his mother is trying to poison his father. Poirot pretends to have stomach cramps, and when he is alone with Hastings, he quickly tells him that Templeton's son is Number Four, as he dabbed up the crumbs with a small slice of bread at the table. The two climb down the ivy and arrive at their flat. The two are caught by a trap; a matchbox filled with a chemical explodes knocking Hastings unconscious and killing Poirot.
Another shock greets Hastings shortly after the funeral; John Ingles had fallen overboard on his boat to China, but Hastings knew this to be murder, by Claud Darrell, Number Four himself. After being warned twice by a disguised Number Four and Countess Rossakoff to leave for South America, Hastings is called to a hospital because Ingles's Chinese servant was stabbed and had a message in his pocket for Hastings. The servant managed to say 'Handel's Largo', 'carrozza' and a few other Italian words before dying. He also receives a letter from Poirot saying to leave for South America, as it was part of the plan. The Big Four would think he was leaving and he could 'wreak havoc in their midst'. This is confirmed when a gentleman in a fur coat (Number Four) sends him a letter saying 'You are wise'. Hastings is put on board a ship for Belgium, where he is reunited with his supposedly dead friend, Poirot.
Hastings is shocked, and Poirot states it was to make his death look certain to the Big Four. After several months of preparations, the two set off for Italy to Lago di Carezza with a member of the secret service, who assures Poirot that the Italian, French, and English governments are working in tandem and everything is prepared. On route to the Big Four's hideout, the two stop at a hotel. Upon their arrival at dinner, they see a man jump up from his table, and, upon further inspection, begin fiddling with his bread. Number Four has seen Poirot is alive, and must decide how to act. Number Four, disguised as usual, begins talking to them, not realizing they know his identity. While chatting, the lights go out and Poirot and Hastings are knocked unconscious and dragged away.
They are taken to the headquarters of the Big Four – The Felsenlabyrinth. They are confronted by Ryland, Olivier and Number Four, with Chang Yen being in China, and later Vera Rossakoff. But there is a surprise waiting for them. The man they have captured does not seem to be Hercule Poirot, but his twin, Achille. The man has a deeper voice, has no moustache and has a scar on his lip.
He makes the four people aware that the mountain has been cordoned off, and that the police are about to raid the headquarters. Knowing their defeat, the three members retreat to a laboratory and Vera decides to bargain with Poirot. He claims that he can bring the dead back to life, and she says that she will save them if he returns her dead child. The three run out of the mountain just as it explodes, in which Ryland, Olivier and Number Four are killed.
Hastings awakes to yet another surprise. Achille Poirot did not exist – it was Hercule Poirot in disguise all along. He manages to give the countess her child back, who was really left in an orphanage, and the newspapers reveal that Li Chang Yen, the famous Chinese politician, has committed suicide. The story ends with Poirot lamenting that all his other cases will seem boring and tame compared to this case.
- Hercule Poirot. The famous private investigator. Having tired of his life in England and dealing with trivial matters, he is tempted to move to Brazil. He has received a monetary offer too good to refuse.
- Arthur Hastings. Poirot's sidekick in two earlier novels and two short stories. This is his return to the series following The Murder on the Links (1923). In that novel Hastings was planning to marry "Cinderella" and move with her to Argentina. Here we learn that he did as planned and has grown prosperous from ranching. Eighteen months later, he returns to London to take care of some business and to visit Poirot. He briefly works as a secretary of Abe Ryland under the alias Arthur Nevill.
- Inspector Japp. This marks the second appearance of the character, following The Mysterious Affair at Styles. He is an inspector of Scotland Yard. He identifies Mayerling.
The Big Four
A multiethnic gang of four persons working towards world domination. They have a secret hideaway in a quarry of the Dolomites. It is owned by an Italian company which is a front company for Abe Ryland. The quarry conceals a vast subterranean base, hollowed out in the heart of the mountain. From there they use wireless communications to transfer orders to thousands of their followers across many countries. The characters comprise typical ethnic and national stereotypes of 1920s British fiction. They are:
- Abe Ryland, the so-called American Soap King. He is stated to be richer than John D. Rockefeller and being the richest man in the world. Early in the novel, Ryland attempts to hire Poirot and invites him to Rio de Janeiro, allegedly to investigate the goings-on in a big company there. Poirot is offered a fortune and is tempted to accept. He eventually declines and the plot point is no longer elaborated. Presumably Ryland intended to recruit him for the organization. He dies when the hidden base of the Four explodes. He represents the power of wealth.
- Madame Olivier, a French woman scientist. She is stated to be a famous nuclear physicist and analytical chemist. Poirot suspects that she has kept secret the true extent of her research with nuclear power. He believes that she has "succeeded in liberating atomic energy and harnessing it to her purpose". She is said to have used gamma rays emitted by radium to perfect a lethal weapon. She is a widow. She used to work with her husband, conducting their research in common until his death. She is said to look more like a priestess out of the past than a modern woman. She dies when the hidden base of the Four explodes. She represents scientific research devoted to political goals.
- Li Chang Yen, the Chinese leader and mastermind of the group, said to have the finest criminal brain ever known. He is an unseen character who never sets foot out of China, but is discussed often by other characters. He is driven by his own lust for power and the need to establish his personal supremacy. He lacks the military force to pursue conquest by traditional means, but the 20th century is stated to be a century of unrest which offers him other means towards him goal. He is said to have unlimited money to finance operations. His methods include bribery and propaganda. He controls a "scientific force more powerful than the world has dreamed of". It is said that "the men who loom most largely in the public eye are men of little or no personality. They are marionettes who dance to the wires pulled by a master hand, and that hand is Li Chang Yen's". He is the power behind the throne of the East. He is the embodiment of Yellow Peril. His plots are said to include worldwide unrest, labour disputes in every nation, and revolutions in some of them. Elsewhere it is explained that he is a mandarin and lives in a palace of his own in Peking. He oversees human subject research on coolies, with no regard for the death and suffering of his research subjects. He commits suicide at the end.
- Claude Darrell, known as the Destroyer. He is an obscure English actor and a master of disguise. He is the chief assassin of the group. He appears with ever-changing faces and multiple identities throughout the novel. He can totally transform his physical appearance and his persona. Many of the novel's characters are known or suspected to be among the roles Darrell plays. Darrell is described as being around 33 years old, brown-haired, having a fair complexion, gray-eyed. His height is given at 5 ft. 10 in (1.78 meters). His origins are mysterious. He played at music halls, and also in Repertory plays. He has no known intimate friends. He was in China in 1919, but returned to the United Kingdom by way of the United States. He played a few parts in New York; he did not appear on the stage one night, and has never been heard of since. New York police say his is a most mysterious disappearance. Darrell has one weakness that can give his real identity away: when he dines, Darrell habitually rolls pieces of bread into little balls. He dies when the hidden base of the Four explodes. He is also effectively a spy and represents the secret services and intelligence agencies.
- Achille Poirot, Hercule's supposed twin brother. He seems to be based on Mycroft Holmes, sibling to Sherlock Holmes. Both characters are equally brilliant to their more famous siblings but too indolent to accomplish much. Achille lacks a mustache and is described by Hercule as his less handsome twin. Achille is later revealed to be Hercule Poirot himself in disguise.
- Countess Vera Rossakoff. A flamboyant, eccentric and devious Russian aristocrat who currently has no personal fortune. She previously met Poirot in The Double Clue, where Poirot was smitten with her. She is an agent of the Four who later becomes a double agent. Vera can be seen as Poirot's Irene Adler—they are the only women to catch the eyes of their respective detectives. The character will return for a third and final appearance in The Capture of Cerberus. In this novel she also uses the alias Inez Véroneau. She is both a friend and an adversary to Poirot. She is employed as a secretary by Madame Olivier.
- Joseph Aarons. A recurring character, who first appeared in The Murder on the Links. He makes appearances in other Poirot tales as well. He is a theatrical agent, so he helps Poirot identify actor Claude Darrell.
- Ah Ling. Chinese servant to Mr Paynter. Inspector Japp's favorite suspect for the murder.
- Betsy Andrews. The housekeeper of Jonathan Whalley. She was the one who discovered the corpse and screamed in shock.
- Colonel Appleby. The American secretary of Abe Ryland.
- Professor Borgonneau. A Parisian scientist who had contact with John Halliday prior to his disappearance.
- Mr Bronson. The ranch manager of Hasting's ranch in Argentina. He sends a message of bad news to his boss.
- Mademoiselle Claude. One of two assistants to Madame Olivier.
- Pierre Combeau. An old friend of Poirot who happens to owe the detective a favor. He does as Poirot asks him, pulling the emergency cord in the Paris-Calais train. This act allows Poirot to leave the stopped train unobserved.
- Sydney Crowther. The Right Honourable Home Secretary. Another friend who owes Poirot a favor. He recommends Hastings as a secretary to Abe Ryland. Ryland was working in England at the time and was looking for a new secretary. He later introduces Poirot to Monsieur Desjardeux, the Prime Minister of France.
- Sonia Daviloff. Niece and housemate of Dr Savaronoff. She is set to inherit Savaroff's fortune from Madame Gospoja once he dies.
- Deans. The valet to Abe Ryland. He is English-born but has spent years in the United States. He follows his boss in his stay to England.
- Monsieur Desjardeux. The Prime Minister of France. Poirot discusses the matter of the Big Four with him.
- Austen Foly, alias Austen Lee. An unseen character, one of the suspects for the real identity of the Destroyer. He originated in a good family. Always had a taste for acting and distinguished himself in that way at Oxford. Brilliant war record. An enthusiast on criminology. He had a nervous breakdown as the result of a motor accident three and a half years before, and has not appeared on the stage since. His present whereabouts are unknown. Age 35, height 5 ft 9 in (1.75 m), complexion fair, eyes blue, hair brown.
- Robert Grant. Also known as Abraham Biggs. A man-servant to Jonathan Whalley of a "rough" background.He is a former prison convict Questioned for the murder and arrested as a suspect.
- John Halliday. A scientist who visited Paris for a conference and disappeared.
- Mrs Halliday. Wife of the missing John Halliday. Has no idea what happened to her husband or why.
- Mr Halsey. The man who arranged Poirot's interview with John Ingles.
- Captain Harvey. A young agent of the British Intelligence Service. He brings the news that China is politically isolated, that the Big Four will meet in Italy, and that the British, French, and Italian governments have joined forces against. With Poirot as the head of the joined operation.
- Monsieur Henri. One of two assistants to Madame Olivier.
- Hodgson. McNeil and Hodgson are Poirot's solicitors.
- John Ingles. A retired civil servant of reportedly mediocre intellect. He is an expert on China and all things Chinese. He informs Poirot of the identity of Li Chang Yen.
- James. The footman of Abe Ryland.
- Captain Kent. A member of the United States Secret Service. He investigates the disappearance of Mr Halliday. He prefers the British laws on alcoholic beverages to those of his own country. He is frustrated with Prohibition.
- Félix Laon. A tall, thin man who attacks Hastings in the man's hotel room in Paris. In the scuffle, Laon appears to lose his wallet. But it is hinted that the wallet was planted for Hastings to find.
- Arthur Leversham. Author of a mysterious letter addressed to Abe Ryland.
- Ernest Luttrell. An unseen character, one of the suspects for the real identity of the Destroyer. Son of a Northern England parson. He was expelled from his public school. Went on the stage at the age of twenty-three. Addicted to drugs. Supposed to have gone to Australia four years before. Cannot be traced after leaving England. Age 32, height 5 ft. 10 in. (1.55 meters), clean-shaven, brown-haired, nose straight, complexion fair, eyes gray.
- Miss Martin. The auburn-haired stenographer of Abe Ryland. Hastings, who is still married, is charmed with her. This is a continuity nod to Hastings having a soft spot for auburn-haired women. Back in The Mysterious Affair at Styles, Hastings was charmed with auburn-haired Cynthia Murdoch and proposed to her. This would letter become a running gag in the series, with Poirot often teasing Hastings. Whenever Hastings suggests the innocence of a young, beautiful, and female murder suspect, Poirot slyly asks, "Does she have auburn hair?" Miss Martin confesses to him that she opened a mysterious letter of their boss.
- John St. Maur. An unseen character, one of the suspects for the real identity of the Destroyer. He has an assumed name, his real name is unknown. Believed to be of cockney extraction. Used to be a child actor. Did music hall impersonations. Has not been heard of for three years. Age, about 33, height 5 feet 10 in (1.55 meters), slim build, blue eyes, fair colouring.
- Mr Mayerling. A former member of the Secret Service and a victim of the Big Four. He dies in Poirot's apartment.
- Mr McNeill. McNeil and Hodgson are Poirot's solicitors. McNeill informs Hastings that they have located Flossie Monro.
- Inspector Meadows. A representative of the Moretonhampstead police who investigates the death Jonathan Whalley. He is an old friend of Inspector Japp who has recommended Poirot to him. He is willing to have Poirot involved in the case.
- Mickey. Son of Mrs Templeton from a previous marriage and stepson of Mr Templeton. He is described as mentally-deficient. He blurts out unpleasant suggestions concerning his mother,. He has a nervous habit reminiscent of Claude Darrell.
- Flossie Monro. An old friend of Claude Darrell. She has bleached blonde hair and a preference for Max Factor and monogrammed shirts. She provides to Poirot information about a personal habit to Darrell that can be used to identify him, regardless of his disguise.
- Mabel Palmer. A hospital nurse. She approaches Poirot to express her suspicions of foul play at the Templetons' residence.
- Mr Paynter. A 55-year-old bachelor. He invited a young nephew to settle in his home. The nephew, an artist, accepted. Paynter then died in an "accident" within his own room.
- Gerald Paynter. Nephew and heir to Mr Paynter. He is an artist, described as being "wild and extravagant". Inspector Japp finds him typical for an artist. He inherits the estate of his deceased uncle.
- Mrs Pearson. Poirot's landlady and housekeeper. Her tasks include opening the door, handling his correspondence, recording phone messages. She does not otherwise speak.
- Dr Ridgeway. Poirot's physician.
- Dr Quentin. The physician blamed for the death of Mr Paynter.
- Mr Saunders. The man who arranged for former convict Robert Grant to find a job once released from prison. He is said to look like a preacher, albeit with a broken front tooth. He has a tendencty to mince his words when speaking.
- Dr Savaronoff. The world's second-best chess player. Number Four masquerades as him in London, where he was challenged to a game by an American champion. He is named as the recipient of Madame Gospoja's fortune, who was herself the widow and sole heiress of a sugar profiteer of the Russian Empire. The real Dr Savaronoff was a Russian Revolutionist who died at the hands of the Bolsheviks. Number Four assumes his identity to steal his inheritance.
- Mr Templeton. An older gentleman who fell ill during his meal. The reason of his illness is undetermined.
- Mrs Templeton. Wife of Mr Templeton. Poirot narrates a story to her about a wife who poisoned her husband and what happened to her. She is increasingly nervous on hearing the tale.
- Dr Treves. He hosts a dinner at the home of the Templetons. During the dinner, Poirot falls ill.
- Jonathan Whalley. Another victim of the Big Four. He is murdered in his own residence, Granite Bungalow in the village of Hoppaton, Devon. He had written to John Ingles, requesting money to escape from the Big Four.
- Gilmour Wilson. A youthful American chess champion. He challenged Dr Savaronoff to a game and died while playing. Poison is the suspected cause of death.
- Dr Bolitho. The usual physician for Mr Paynter, away on holiday at the time of Paynter's demise.
These characters are all described by Zemboy.
- An unnamed doctor. His role is to pronounce the death of Mayerling.
- An unnamed man from Hanwell Asylum. He claims Mayerling was a recently-escaped inmate of the asylum.
- An unnamed Chinese servant of John Ingles. His only distinguishing feature is his apathetic face.
- An unnamed elderly man from the rural area surrounding Hoppaton. He gives Poirot and Hastings instructions on how to locate the Granite Bungalow, He is also the one to inform them that Jonathan Whalley has been murdered.
- A group of Slavs and other foreigners who visit Poirot in his flat for mysterious reasons. Described as looking extraordinary and repulsive.
- An unnamed dark man, thin and middle-aged. He approaches Hastings in a small restaurant in Soho. Strongly "advising" the man to leave England and return to South America.
- An unnamed Chinese man, former servant of John Ingles. He delivers a cryptic message to Hastings and then dies at St. Giles Hospital of London.
- An unnamed officer of the steamship Ansoria which was transporting Hastings to South America. He wakes Hastings up to inform him that he is about to change ships. His new destination is Belgium.
- An unnamed Belgian manservant, elderly in years. The apparent servant of Achille Poirot in his villa. He receives Hastings on behalf of his employer.
- An unnamed customer of a hotel restaurant at Bolzano, South Tyrol, Italy. He has a nervous habit reminiscent of Claude Darrell. Encountering Poirot by chance, the man springs up from his seat and exits in a hurry.
- An unnamed waiter of a hotel restaurant at Bolzano, South Tyrol, Italy. He collides with the speedily exiting customer.
Jerry Speir points out that the novel departs from the formula of the Hercule Poirot series. The novel is not set in the manor house or a rural area like a number of its predecessors, nor do the characters represent the British gentry. The villains are a gang of international criminals, controlling a secret, global organization. Their goals include the so-called disintegration of human civilization. They control an unspecified "scientific force", a weapon of some kind. Speir speculates that they could hold the secrets to gravity or nuclear power.
Armin Risi agrees that this was to be the great case of Poirot's life, as the character himself claims that all other cases will seem tame by comparison. Poirot does not track down a murderer; he must face and expose a supranational association of high-ranking personalities who are working towards world domination. Risi sees the book as a work of secret history which was inspired by the events and causes of World War I and the October Revolution (the novel was presumably written in 1924 or 1925; see the biographical remark below). The basic scenario of the novel has secret powers (the Four) influencing humanity and the course of history. To Risi it seems to be Agatha Christie's warning about real-life organizations doing the same. He points out that Christie herself may not have been an objective historian. She was a member of the high society in the British Empire. But this fact possibly gave her access to first-hand observers of world politics and the secret affairs behind them. During the interwar period, World War I and the October Revolution were still significant topics of conversation. He theorizes that Christie may have learned of organizations of conspirators active in the era, at least those active in the City of London. There were already rumors that secret forces were planning World War II or even World War III.
The novel describes the Four: "There are people, not scaremongers, who know what they are talking about, and they say that there is a force behind the scenes […] A force which aims at nothing less than the disintegration of civilization. In Russia, you know, there were many signs that Lenin and Trotsky were mere puppets whose every action was dictated by another's brain." Elsewhere in the novel, Poirot states that their aim was to destroy the existing social order, and to replace it with an anarchy in which they would reign as dictators. The menace of the Four seems to originate in China. One of the murder victims of the Four is seafarer John Whalley, who had returned from Shanghai. It is hinted this voyage indirectly caused his death, since he encountered something sinister in China. Another victim is wealthy globetrotter Mr Paynter whose remains were burned in his own fireplace. Near the body was a cryptic message in ink: "Yellow Jasmine". Paynter was writing a book called The Hidden Hand in China, which seems to provide the motive for his murder. The Big Four are at some point testing new technology and weapons. A powerful wireless installation is used to concentrate energy "far beyond anything so far attempted". It is capable of focusing a beam of great intensity and destructive power. It was tested against torpedo boats of the Royal Navy which were completely destroyed.
James Zemboy observes that this novel lacks the unity of plot of a proper novel. It is a series of episodes, only unified by the theme of Hercule Poirot investigating and uncovering the identity of one of the villains. The Big Four themselves are unique characters, each one representing a personification of evil. But Zemboy finds these characters lacking in traits to make them amusing, engaging, or personally interesting. The minor characters are not unique. They are generic messengers or information providers. John Ingles serves only to provide information on Li Chang Yen, Flossie Monro is only significant in providing a single clue, and Sonia Daviloff only serves to show Poirot the position of the chess table.
Zemboy finds the book atypically boring for Christie. He believes that readers whose only exposure to her work is this novel, will be unlikely to pursue more of her books. The episodic nature of the book could have led to it being twice as long or half as long, without making any difference. The pattern of the novel is a series of dangerous encounters and failures to catch the criminals. Poirot repeatedly sets traps for the enemy. Repeatedly the enemy knows in advance and does not fall for them. On the other side, the Big Four set traps for Poirot. He evades most of them, only to find that the Four anticipated his moves as well. He does fall for some "real" traps.
The novel offers more information on Hastings. He did marry his "Cinderella" and did move to South America. Both events were mentioned briefly in The Murder on the Links. The novel could also serve as a finale for Poirot. At the end, he decides to retire to the countryside and to pursue his new hobby of growing vegetable marrows. This seemingly contradicts The Murder of Roger Ackroyd where Poirot was already in retirement and growing vegetable marrows. Zemboy suggests that The Big Four was written before The Murder of Roger Ackroyd. He notes a reference in Agatha Christie: An Autobiography where the writer notes that between The Man in the Brown Suit and The Secret of Chimneys, she had written another novel.
Literary significance and reception
The Times Literary Supplement review of the book publication struck a positive although incorrect note in its issue of 3 February 1927 when it assumed that the different style of the book from its immediate predecessor, The Murder of Roger Ackroyd, was a deliberate ploy: "M. Poirot, the Belgian detective who has figured in others of Mrs Christie's tales, is in very good form in the latest series of adventures. The device which made "Who killed Roger Ackroyd?" (sic) such a puzzling problem for the reader of detective fiction is one that a writer cannot easily employ a second time, and indeed the present story is not so much the clearing up of a mystery as a recital of Poirot's encounters with one of those familiar groups of international crooks of almost unlimited power who seek to dominate the world." Hastings was described as "dense as ever".
The New York Times Book Review of 2 October 1927 outlined the basics of the plot and stated "'Number Four' remains a mystery almost to the end. This, of course, makes it more difficult for the detective to guard against attack and to carry on his investigation, and it provides most of the thrills of the story."
The reviewer in The Observer of 13 February 1927 did not expect originality when reading a book dealing with the themes of The Big Four, but did admit that "When one opens a book and finds the name Li Chang Yen and is taken to subterranean chambers in the East End 'hung with rich Oriental silks', one fears the worst. Not that Mrs Christie gives us the worst; she is far too adroit and accomplished a hand for that. But the short, interpolated mysteries within the mystery are really much more interesting than the machinations of the 'Big Four' supermen." The conclusion of the book was "pretentious" and "fails to be impressive" and the reviewer summed up by saying, "the book has its thrills – in fact, too many of them; it seeks to make up in its details what it lacks in quality and consistency."
The Scotsman of 17 March 1927 said, "The activities of Poirot himself cannot be taken seriously, as one takes, for example, Sherlock Holmes. The book, indeed, reads more like an exaggerated parody of popular detective fiction than a serious essay in the type. But it certainly provides plenty of fun for the reader who is prepared to be amused. If that was the intention of the authoress, she has succeeded to perfection".
Robert Barnard: "This thriller was cobbled together at the lowest point in Christie's life, with the help of her brother-in-law. Charity is therefore the order of the day, and is needed, for this is pretty dreadful, and (whatever one may think of him as a creation) demeaning to Poirot."
Connection to other works
Jeremy Black, a historian, points out that a number of Agatha Christie's novels of the interwar period record the standard fears of affluent society in the era. She added the "paranoid" conviction of an underlying conspiracy. This is an element present in her literary work and absent in the adaptations of Agatha Christie for television and film.
Black adds that Christie's work is, in its way, typical of the literature of the interwar period, much of which reflected a concern about foreign threats and links between domestic and international challenges. The Big Four, the characters, are positioned as the hidden cause and connecting threat between the world-wide unrest, labour disputes, and the revolutions of the period—in particular, the October Revolution, with Vladimir Lenin and Leon Trotsky described as their puppets. The Big Four also have advanced technology in their arsenal.
Li Chang Yen is both a creature of sinister Orientalism and an echo of an earlier literary character: Fu Manchu by Sax Rohmer. The character was described as "the greatest genius which the powers of evil have put on the Earth for centuries", the foe of the British Empire and British civilization in general. The character combined great cruelty with advanced scientific research. In The Mystery of Dr. Fu-Manchu (1913), the eponymous character is presented as a figure behind Anti-Western actions in British Hong Kong and Chinese Turkestan. He is striking against Western politicians and administrators who are aware of the secret geopolitical importance of Tonkin, Mongolia, and Tibet, using these areas as a keyhole to the gate of the Indian Empire.
Fu Manchu's agents were omnipresent even in England. His organization was likened to a yellow octopus with Fu Manchu as its head with dacoits and thugs as its tentacles. These agents killed secretly, swiftly, and leaving no clue behind. These were the literary predecessors of the Four and their agents.
David Suchet, who played Poirot for ITV from 1989 to 2013, had a different suggestion as to the origins of the Big Four. He found them to be an evil counterpart of The Four Just Men series by Edgar Wallace. He agrees, however, that Li Chang Yen was inspired by Fu Manchu.
Development of the novel from short stories
This novel began as a series of twelve short stories (eleven in the US).
First publication of stories
The structure of the book is different from that of most Christie novels in that The Big Four is a series of short cases involving the Big Four villains rather than the investigation of a single crime. The novel is derived from a series of linked short stories that first appeared in The Sketch magazine in 1924 under the sub-heading of The Man who was No. 4, then amalgamated into one narrative.
The original publication details of the stories (which were carried without illustrations) are as follows:
- The Unexpected Guest: First published in issue 1614 of The Sketch on 2 January 1924. This formed the basis for chapters 1 and 2 of the book – The Unexpected Guest / The Man from the Asylum.
- The Adventure of the Dartmoor Bungalow: First published in issue 1615 on 9 January 1924. This formed the basis for chapters 3 and 4 of the book – We hear more about Li Chang Yen / The Importance of a Leg of Mutton.
- The Lady on the Stairs: First published in issue 1616 on 16 January 1924. This formed the basis for chapters 5 and 6 of the book – Disappearance of a Scientist / The Woman on the Stairs.
- The Radium Thieves: First published in issue 1617 on 23 January 1924. This formed the basis for chapter 7 of the book with the same title.
- In the House of the Enemy: First published in issue 1618 on 30 January 1924. This formed the basis for chapter 8 of the book with the same title.
- The Yellow Jasmine Mystery: First published in issue 1619 on 6 February 1924. This formed the basis for chapters 9 and 10 of the book – The Yellow Jasmine Mystery / We investigate at Croftlands.
- The Chess Problem: First published in issue 1620 on 13 February 1924. This formed the basis for chapter 11 of the book with the slightly revised title of A Chess Problem. Chapter 11 from the novel has also been published as stand-alone short story in reprints.
- The Baited Trap: First published in issue 1621 on 20 February 1924. This formed the basis for chapters 12 and 13 of the book – The Baited Trap / The Mouse walks in.
- The Adventure of the Peroxide Blonde: First published in issue 1622 on 27 February 1924. This formed the basis for chapter 14 of the book with the slightly revised title of The Peroxide Blonde.
- The Terrible Catastrophe: First published in issue 1623 on 5 March 1924. This formed the basis for chapter 15 of the book with the same title.
- The Dying Chinaman: First published in issue 1624 on 12 March 1924. This formed the basis for chapter 16 of the book with the same title.
- The Crag in the Dolomites: First published in issue 1625 on 19 March 1924. This formed the basis for chapters 17 and 18 of the book – Number Four wins the trick / In the Felsenlabyrinth. It was also the final Poirot story that Christie wrote for The Sketch.
In the United States, the majority of The Big Four first appeared in the Blue Book Magazine insofar as the publication of the book version occurred partway through the publication of the stories in the Blue Book. In addition, the version published in the Blue Book was that of the book text (with small abridgements) and not that of the 1924 UK Sketch text. It can therefore be viewed as a serialisation of the book rather than a reprinting of the short stories. All of the instalments carried an illustration. The artist for the first five instalments was L. R. Gustavson, while William Molt provided the illustrations for the latter six.
The publication order was as follows:
- The Unexpected Guest: First published in the March 1927 issue (Volume 44, Number 5) which formed chapters 1 and 2 of the book.
- The Dartmoor Adventure: First published in the April 1927 issue (Volume 44, Number 6) which formed chapters 3 and 4 of the book.
- The Lady on the Stairs: First published in the May 1927 issue (Volume 45, Number 1) which formed chapters 5 and 6 of the book.
- The Radium Thieves: First published in the June 1927 issue (Volume 45, Number 2) which formed chapter 7 of the book.
- In the House of the Enemy: First published in the July 1927 issue (Volume 45, Number 3) which formed chapter 8 of the book.
- The Yellow Jasmine Mystery: First published in the August 1927 issue (Volume 45, Number 4) which formed chapters 9 and 10 of the book.
- The Chess Problem: First published in the September 1927 issue (Volume 45, Number 5) which formed chapter 11 of the book.
- The Baited Trap: First published in the October 1927 issue (Volume 45, Number 6) which formed chapters 12 and 13 of the book.
- The Peroxide Blonde: First published in the November 1927 issue (Volume 46, Number 1) which formed chapter 14 of the book.
- The Enemy Strikes: First published in the December 1927 issue (Volume 46, Number 2) which formed chapters 15 and 16 of the book.
- The Crag in the Dolomites: First published in the January 1928 issue (Volume 46, Number 3) which formed chapters 17 and 18 of the book.
The announcement of the publication of these stories in the Blue Book had been made as far back as November 1925 when, at the end of their publication of The Lemesurier Inheritance, the editors announced, "Further stories by Agatha Christie, who is firmly established in the front line of writers of mystery and detective tales, will appear in forthcoming issues of The Blue Book Magazine. Watch for The Big Four." The reason for the eventual delay in publication is not known.
Timing of publication in Christie's life
In 1926 Christie was already deeply affected by the death of her mother earlier in the year and the breakdown of her marriage to Archibald Christie. Her brother-in-law, Campbell Christie, suggested compiling the Sketch stories into one novel, rather than undergo the strain of composing a completely new novel, and helped her revise them into a more coherent form for book publication. His assistance mainly took the form of revising the beginnings and ends of the stories to make them flow better into a novel – the substance of each story remains the same between the short story version and the novel version. Unlike the later Partners in Crime (1929), the order of the stories was retained.
Around this time, a novel was offered for publication to The Bodley Head and was rejected. No other information exists on this novel, but Zemboy suggests it was The Big Four. His theory continues with Christie's relationship to her new publisher William Collins, Sons. Christie would have realized that The Big Four was an inferior novel and went to work writing The Murder of Roger Ackroyd for the new publisher.
The book was published a few weeks after the disappearance and reappearance of Christie. The resulting publicity over her name caused the new novel to become a sales hit. Sales were good enough to more than double the success of The Murder of Roger Ackroyd. It sold despite not being a traditional murder mystery, being a tale of international intrigue and espionage, and opening the possibility of more spy fiction from Christie.
In 1942, Christie wrote to her agent, Edmund Cork of Hughes Massie, asking him to keep a manuscript in reserve (probably Sleeping Murder) and stated
I have been, once, in a position where I wanted to write just for the sake of money coming in and when I felt I couldn't – it is a nerve wracking feeling. If I had had one MS 'up my sleeve' it would have made a big difference. That was the time I had to produce that rotten book The Big Four and had to force myself in The Mystery of the Blue Train.
This is the second Christie crime book not to carry a dedication, Poirot Investigates being the first.
- 1927, William Collins and Sons (London), 27 January 1927, Hardcover, 282 pp
- 1927, Dodd Mead and Company (New York), 1927, Hardcover, 276 pp
- 1957, Penguin Books, Paperback (Penguin number 1196), 159 pp
- 1961, Pan Books, Paperback (Great Pan G427), 155 pp
- 1964, Avon Books (New York), paperback
- 1965, Fontana Books (Imprint of HarperCollins), paperback, 159 pp
- 1965, Dell Books (New York), paperback, 173 pp
- 1974, Ulverscroft Large-print Edition, Hardback, 414 pp ISBN 0-85456-283-4
- 1984, Berkley Books, Imprint of Penguin Group (USA) (New York), paperback, 198 pp ISBN 978-0-425-09882-0
- 2006, Poirot Facsimile Edition (Facsimile of 1927 UK First Edition), HarperCollins, 6 November 2006, Hardcover, ISBN 0-00-723451-1
The Big Four was released by HarperCollins as a graphic novel adaptation on 3 December 2007, adapted and illustrated by Alain Paillou (ISBN 0-00-725065-7). This was translated from the edition first published in France by Emmanuel Proust éditions in 2006 under the title of Les Quatre.
The novel was adapted for television with David Suchet as Poirot, as part of the final series of Agatha Christie's Poirot. The film premiered on ITV on 23 October 2013 and on PBS on 27 July 2014 in the United States; it also guest-starred Sarah Parish, Patricia Hodge, Tom Brooke, Nicholas Burns, and Simon Lowe. Suchet's former co-stars Hugh Fraser, Philip Jackson, and Pauline Moran reprised their roles as Hastings, Japp, and Miss Lemon (who was added to the proceedings despite not appearing in the novel) after an approximately ten-year absence from the show itself. The episode explains their absence by implying that Hastings has been living on his Argentinian ranch, and Miss Lemon enjoying a quiet life on her own after leaving Poirot's employ. Japp has been promoted to Assistant Commissioner of the Met, and in the episode he assumes the role of Poirot's sidekick, whereas it was Hastings who filled the position in the novel. The guest cast includes Nick Day as Ingles, James Carroll Jordan as Ryland, Patricia Hodge as Madame Olivier, Steven Pacey as Paynter and Sarah Parish as Flossie.
The episode is very loosely based on the novel, considered by writer Mark Gatiss to be "an almost unadaptable mess". Most of the novel's plot points, for instance, have been removed, including the death of Mayerling in Poirot's flat, the radium exploit involving Madame Olivier, Hastings' time as Ryland's secretary, and Poirot's subterfuge as Achille, his purported sibling. Instead, prominence is placed on the leg of mutton case, the chess murder, and the yellow jasmine (in the adaptation, gelsemine) mystery. The cast of characters is pared down considerably as a result of these omissions, and this includes the deletion of Countess Vera Rossakoff. The most significant changes involve the villains themselves. In the novel, all four members of the Big Four are indeed guilty of their crimes, although they live separate lives. In the adaptation, Olivier and Ryland are stalwarts of a Peace Party founded by Li Chang Yen, who is a pacifist rather than a dissident. Olivier and Ryland are each connected to one of the murders, and quickly vanish when suspicion is cast upon them. It is revealed at the end, however, that Li Chang Yen, Olivier and Ryland are all innocent, and were deliberately framed by the sole villain, Claud Darrell. Darrell is one of several disguises of Albert Whalley, also including Paynter's physician, Dr Quentin. Whalley is a brilliant but insane character actor who orchestrates the entire Big Four setup, feeding the press with sensational clues and threatening letters and killing his victims to implicate the Peace Party members (whom he then kidnaps and drugs with immobilising gelsemine) thus validating the organisation's existence. His motive in doing all of this is to attract the admiration of Flossie Monro, who becomes an unrequited lover whom he showers with anonymous gifts and cards expressing his love for her. It transpires that Flossie told him he wasn't good enough for her in the past, and the mad scheme is an attempt to make himself the international celebrity he believes she desires. Unlike in the novel, the climactic showdown does not take place in an elaborate headquarters within a mountain, but in the old repertory theatre where Darrell and Flossie had acted as young adults. There is no deadly explosion, either, although Darrell attempts to set off dynamite; only Poirot reminding Darrell that he cannot kill Flossie persuades him to dismantle the explosive. Instead when the madman tries to shoot Poirot, he is killed by the journalist Lawrence Boswell Tysoe (an original character not in the novel), who drops a safety curtain on him. Li Chang Yen (in absentia), Olivier and Ryland escape death, and continue their work as Peace Party advocates; Flossie (who was murdered in the novel and therefore played no role in the solution) also survives her original fate.
As in the novel, Poirot does stage his own death. When Darrell learns that Poirot is getting close to the truth, he tries to lure him into a flat rigged with explosives, observing him in the guise of an old woman. Poirot spots the danger just in time, and manages to escape the scene before the explosives go off, planting his walking stick at the scene to create the impression that he died in the blast. Japp notifies Hastings and Miss Lemon, and together with George the valet they attend Poirot's "funeral", none of them—with the exception of Japp, who appears at the denouement—having any idea that he survived until after the final showdown with Darrell. Poirot later explains that the charade was necessary to make Darrell overconfident, and thus reckless enough to unravel his own schemes. The episode ends with Poirot reuniting with his old friends. This marks the final appearances of Philip Jackson and Pauline Moran as their respective characters.
- The Publishers' Circular and Booksellers Record 15 January 1927 (Page 1)
- Cooper, John; Pyke, B.A. (1994). Detective Fiction – the collector's guide (Second ed.). Scholar Press. pp. 82, 86. ISBN 0-85967-991-8.
- Marcum, J S (May 2007). "American Tribute to Agatha Christie: The Classic Years 1920s". Retrieved 13 October 2015.
- The English Catalogue of Books Vol XII (A– L: January 1926 – December 1930). Millwood, New York: Kraus Reprint Corporation. 1979. p. 316.
- Bunson, Matthew (2000). "The Big Four". The Complete Christie: An Agatha Christie Encyclopedia. Simon & Schuster. ISBN 978-0671028312.
- Zemboy, James (2008). "The Big Four (1927)". The Detective Novels of Agatha Christie: A Reader's Guide. McFarland & Company. ISBN 978-0786451685.
- Risi, Armin (2004). "The Big Four". TranscEnding the Global Power Game: Hidden Agendas, Divine Intervention, and the New Earth. Light Technology Publishing. ISBN 978-1622337132.
- Boltanski, Luc (2014). "Theme and variations". Mysteries and Conspiracies: Detective Stories, Spy Novels and the Making of Modern Societies. John Wiley & Sons. ISBN 978-0745683447.
- Speir, Jerry (2001). "The Big Four". The Bedside, Bathtub & Armchair Companion to Agatha Christie. Continuum International Publishing Group. pp. 30–32. ISBN 978-0826413758.
- The Times Literary Supplement 3 February 1927 (Page 78)
- The New York Times Book Review 2 October 1927 (Page 30)
- The Observer, 13 February 1927 (page 5)
- The Scotsman, 17 March 1927 (page 2)
- Barnard, Robert (1990). A Talent to Deceive – an appreciation of Agatha Christie (Revised ed.). Fontana Books. p. 188. ISBN 0-00-637474-3.
- Black, Jeremy (2004). "The Geopolitics of James Bond". Understanding Intelligence in the Twenty-First Century: Journeys in Shadows. Routledge. p. 136. ISBN 978-1135769741.
- Suchet, David (2013). "It is never finished with a murder. Jamais!". Poirot and Me. Hachette. ISBN 978-0755364206.
- The Blue Book Magazine Volume 42, Number 1. November 1925
- Morgan, Janet (1984). Agatha Christie, A Biography. Collins. p. 163. ISBN 0-00-216330-6.
- "TV review: Suchet splendidly wraps up Poirot". SFGate. Retrieved 17 May 2015.
- "Mark Gatiss on Twitter". Twitter. Retrieved 17 May 2015.
- Pendergast, Bruce (2004), "Racism? Yes, Sorry to Say", Everyman's Guide to the Mysteries of Agatha Christie, Trafford Publishing, ISBN 978-1412023047
- The Big Four at the official Agatha Christie website