When a Jamaican bus driver is garroted in the middle of the night, there is speculation that racism is the motive. But when the same grisly fate befalls an Asian man and then a white man, it becomes clear that a female serial killer with a different obsession is at work.

Still mourning her mother's recent violent death, DCI Jo Pollitt of the Southwark London Metropolitan Police must now focus on this high-priority case. Even with the help of a pathologist, a profiler, and publicity from a true-crime TV show, the culprit remains elusive. Pollitt takes emotional refuge in her relationship with Cilla, whom she's known since childhood, but the stress, both personal and professional, keeps building.

However, when Pollitt learns a civilian has captured video of the most recent murder, it reveals the police might be on the wrong track. As the case begins to unravel, Pollitt realises that everything she believed is now in jeopardy and time is ticking before the killer strikes again . . .