Detective Sergeant John Niven was adopted, and believed he had adjusted to that long ago. But a personal crisis makes him wonder about his origins, his career and his future with Gill, his girlfriend. Simultaneously, he is hunting a killer who might well be a fellow policeman and, when Gill becomes inexplicably entangled, Niven sinks deeper into the case. When he identifies a break in the investigation it helps him unravel the killer's purpose and, he believes, the killer's identity. In a final confrontation, it appears the fates have been cruelly mocking him and it seems he really is an orphan of chance.