Stonemason Andrew Knightley is pushed under a London Underground train during the morning rush hour. DI Max Arnold and his partner, DS Priya Shamsie, together build a picture of a lonely, devout, and troubled man who believed a spirit was leaving him vengeful Biblical messages. But the killer is flesh and blood, and a more earthly explanation may be found in the truth of Knightley's life.

A well-liked security guard is found stabbed to death, leaving behind his terminally ill wife. Could this pillar of the community have been killed in a drug deal gone wrong, as the evidence initially suggests? Max and Priya discover that the victim had an unsavoury past filled with violence, racism, and hooliganism, and that his death is the latest tragedy in a decades-old cycle of violence.