A serial killer is loose in London, and the only one who might help catch them is already behind bars. DI Henley of the Serial Crimes Unit is called to investigate a series of gruesome discoveries along the River Thames, only to find that the murders bear the chilling hallmarks of Peter Olivier, the notorious Jigsaw Killer. The complication: Olivier is already imprisoned, and Henley herself was the one who put him away. Despite her reluctance, Henley must seek Olivier's assistance to identify and stop a copycat killer before more victims are found, but Olivier has his own agenda.

The premise sets up a high-stakes thriller where a detective must confront a dangerous incarcerated killer to stop a copycat. The narrative structure suggests a focus on suspense and psychological tension as the protagonist navigates the complex relationship with Olivier. The pacing is likely to be fast-paced, driven by the urgency of preventing further murders. The thematic exploration may delve into the nature of evil, the thin line between hunter and hunted, and the personal toll of such investigations.