Sam is shaken when she has to look into the death of a very dear friend, Dr. Annabelle Evans, a Cambridge professor. She was found in her home, badly beaten in what appears to be a botched burglary attempt. The police immediately focus on the husband as the likely killer but Sam suspects that an altercation at a local restaurant during the May Ball, where a waiter spilled wine on Annabelle and was fired on the spot, may provide another suspect. Sam is also intrigued by the relationship some of her students may have had with Annabelle, particularly when she learns her friend may have had a lover. In her personal life, Sam has moved on. Her sister Wyn has relocated to Ireland and Peter Ross has also been transferred. She does however run into an old friend who also happens to be an acquaintance of her business partner Trevor.

As Sam, et al continue to look into Annabelle's violent murder, another woman is similarly assaulted.

Harry investigates the death of a woman who drowned in a backyard pool. She was apparently struck on the side of the head and her husband claims that her expensive necklace is missing. Leo and Nikki investigate the death of Lucie Philips, a kidnap victim who was taken a week previously. The girl's father tried to pay the ransom but the money was never collected leading the police to believe that the kidnappers may have had other motives. They also investigate the murder of a pizza deliveryman that has similarities with the Philips crime scene. A third murder leads the police to suspect that they may be seeing the work of a serial killer. Nikki's grandmother dies bringing her into contact with her estranged father.

Leo and Nikki find yet another victim who was apparently bound and buried alive. However, they continue to have difficulty finding a common link among all of the victims. The investigation focuses on the editor of a philosophical journal who had an intellectual disagreement with one of the victims but the case is more complex than first imagined. Harry discovers that his drowning victim was pregnant which may have indirectly contributed to her death. Nikki's father is released from prison and promptly disappears.

Harry and Nikki deal with the case of a young woman who is found dead in an animal shelter. Her dead body has obviously been posed and the autopsy reveals she may have been tortured before death. Information from police intelligence suggests that they may be dealing with a group of radical animal rights activists. It all becomes quite personal for Harry when Nikki is taken prisoner. It's also a difficult time for Leo who has been asked to appear before a medical council hearing and testify on the propriety of a close friend's medical research. Harry has been offered a prestigious chair at an American university, but has had difficulty discussing the issue with his colleagues, especially Nikki.

Harry and the police desperately search for Nikki as they continue to find more bodies. The animal rights activists' target is a well known pharmaceutical firm that is undertaking research on behalf of the government. Leo finally decides on a course of action in testifying at the medical council hearing.