One cold spring morning in County Cork, two fishermen find a bundle of rags floating in the Blackwater River: the mutilated corpse of a retired music teacher. His hands and feet are bound, and his neck bears the mark of a garrotting wire.

The Garda want to wrap this case up before the press get hold of it. But when a second man is found murdered, the body bears all the same marks as the first.

And Detective Superintendent Katie Maguire fears this case carries the hallmark of a serial murderer...