Victim, suspect, policeman. When the lines blur, who do you trust?

When two bodies surface in the garden of a rented house in North London, Forensics discover fingerprints which link back to an unsolved crime that no one in the Metropolitan Police wants to remember.

More than a decade ago, in an isolated holiday cottage in Sussex, a family was found brutally slaughtered. The prime suspect was Callum Carmichael, the father of the family and a police officer from the Met's own ranks. But without enough evidence to arrest him, the case was hushed up and the trail left to go cold.

Now, with fresh proof that the killer is still out there, rookie DC Ebony Willis is sent to find Callum Carmichael. But Carmichael is an unknown entity and, with every piece of information she tells him, she risks leading a dangerous man closer to his prey.