The psychological thriller examines the lives of two hunters -- one is a serial killer who preys on victims in and around Belfast, Northern Ireland, and the other is a female detective drafted from the London Metropolitan Police to catch him. The local authorities have no suspects and no experience with cases involving sexually motivated serial killers; DSI Stella Gibson has. She heads a task force dedicated to solving the crime spree, with a simple motto: Anyone not part of the solution is part of the problem. The killer? He's Paul Spector, a father and a husband leading a double life, as viewers learn from the outset. He's hiding in plain sight, the protagonist in a cat and mouse game that is every police officer's worst nightmare.