It stars Suranne Jones as Linda, a bisexual ex police officer turned sex therapist, who shares a practice in Leeds with her brother-in-law, played by Tristan Gemmill. Her life is complicated by the fact that her husband Richard, her business partner's brother, played by Christian Solimeno, has low fertility and cannot give her the baby she wants. She is all for asking his brother (her business partner) to be a sperm donor, which does not sit well with his wife (Kate Isitt). Linda's husband (Richard) is also not keen on the idea at all but lets Linda go ahead and ask his brother who consents to be a sperm donor. Sexual tension becomes obvious between the pair, and they soon begin sleeping together, with disastrous consequences for all involved, especially Angie (Eva Pope), Linda's ex-lover who is still very much in love with Linda.
Further complications occur with Linda's involvement as a CID consultant in a bizarre spate of murders that centre on erotic asphyxiation and could be linked back to her practice. The murder enquiry is led by Linda's former lover, played by Eva Pope. However Linda is suspicious of the second 'murder' and of Angie, as it all seems a bit too convenient.