A MISSING BOY. Teenager Luke Mullen was last seen getting into a car with an older woman. No one can understand why he has disappeared. His father - a former police officer - knows all too well that the longer he is missing, the more likely he is to turn up dead.

A TERRIFYING VIDEO. Then Luke’s parents receive an anonymous video. It shows their son, eyes wide with terror, as a man advances towards him holding a syringe.

A RACE AGAINST TIME. DI Tom Thorne recognises a psychopath when he sees one. And the scene on the tape chills him to the bone - he knows that a child’s life hangs in the balance and that every minute counts…