TV reporter Dan Groves and Detective Adam Breen are reunited to try to save a young girl who's been abducted by a psychopath, a once brilliant man tormented by war and the death of his best friend and utterly bent on taking his revenge on society. A masked attacker breaks into women's homes, threatens them with a gun, but never speaks and steals nothing of value, only a document bearing their name. He leaves behind a note addressed to Dan, boasting of plans for a great crime, one which will shock the country. A police marksman kills two men in separate but frighteningly similar shootings. Detectives are suspicious, but is it murder? Their only clue is a cryptic password they find hidden at the man's home and a possible motive festering in his past.Another woman is attacked, another document taken, another note left. It claims each contains a code revealing the great crime. And it's growing closer, hour by passing hour. Dan is put under police guard as it becomes clear the man is stalking him. Adam and Dan face baffling questions. Why does the attacker steal only documents bearing the women's names? How to solve the riddles contained in the notes? Code breaking experts are called in to help. But before they can, a young girl is abducted. An intensive manhunt is launched. The battle to solve the clues in the letters grows more frantic. The pressure is intense. But as each riddle is cracked, the man is always one step ahead of the police - until the increasingly desperate search converges on Dartmoor.