Nikki's mental instability worsens, and Harry and Leo are forced to get her psychiatric help. When the true identity of the murderer is discovered, it becomes a race against time to save Nikki's life.

After a preserved female body is discovered buried in a peat moor in Sheffield, DI Sonia Hardwick turns to an archaeologist called Professor Patrick Cain for help. Nikki discovers knife wounds to the hands which the professor believes may indicate a ritual killing as the autopsy on the body is carried out. Leo ends up searching through his archives for a case he dealt with in Sheffield in 1985 that were committed by self-confessed serial killer Karl Bentley. As he examines the body himself he is caught by Nikki and Leo tells him he thinks the body could belong to a woman called Jodie Fisher who went missing at the time.