A young woman, Fiona Holland, has gone missing from a small Irish village. A week later, a gruesome discovery is made in the woods at the valley of Glendalough. The bodies are all young women who disappeared in recent years. D.I. Tom Reynolds and his team are faced with the toughest case of their careers - a serial killer who hunts vulnerable women. Soon the race is on to find Fiona Holland before it's too late.