In Part 1, D.C.I. Thomas Flynn is called upon to solve the riddle of a murder scene without a corpse. When the body is finally discovered, it soon becomes clear that a terrifying serial killer is on the loose. Meanwhile, the detective has issues of his own to contend with when he meets his beautiful half-sister for the first time

In Part 2, D.C.I. Thomas Flynn closes in on the serial killer when a fifth body is found hanging from a fence, and finds his life becoming entwined with that of Ian Stanford, the first victim's husband. The detective's concern for half-sister Milly grows when she reveals she's joined a dating agency - with neither of them realising she's part of the murderer's deadly plan.