The team looks into the death of a terrorist 30 years previously after his daughter receives an anonymous note claiming he was murdered - an investigation that takes them right back to the Greenham Common anti-nuclear protests.

Meanwhile, Sasha agrees to go for dinner with her ex-husband Ned, which he is hoping will lead to a reconciliation.

Tension mounts as Ned and Sasha are forced to work together when the body of a film critic found in a sewer is thought to be linked to the 20-year-old murder of a concept artist, David Straka. As the team interview Straka's contemporaries, groupies and assistants, looking for possible connections between the deaths, they find themselves immersed in the macabre world of the occult. And Griffin's expert knowledge of the history of London and in particular the hidden Fleet River, proves invaluable.

When cold-crime enthusiast Ellen Barker is murdered, a photo of Dan Griffin is found at her house. Griffin is interviewed by the murder team, who realise that Ellen was a friend of his. The senior investigating officer assigned to Ellen’s murder investigation is DCI Grace Mackie, one of Sasha Miller’s contemporaries from their Hendon training. Griffin is convinced that the last case Ellen was looking at could lead to her killer, and heads to Minchampton, where a woman called Sally Tunstall was murdered 25 years ago by local lad Dougie Haynes.