A new murder victim forces the team to consider whether a notorious serial killer has resurfaced after 20 years, or if they are dealing with a copycat. Nikki and Jack investigate a murder bearing all the hallmarks of a notorious serial killer. When Nikki meets Charles Beck, the pathologist who conducted the original post-mortems, she discovers his wife was the suspected fifth victim of the serial killer, but nobody believes him when he claims he knows where to find her body.

The team pieces together the mystery of a man found dead on the shore of the Thames, while the life of a disgruntled criminology professor begins to unravel. The team works on a suspected suicide, but the investigation raises more questions than it answers. Gabriel has an exciting new opportunity, both professionally and personally, and enlists Jack's help. When a disgruntled professor of criminology is passed over for promotion, events take a truly sinister turn and the interview panel begins to be targeted. Could a member of the Lyell be next?