A Question of Identity: Susan Hill

How do you catch a killer who doesn't exist?

One snowy night in the cathedral city of Lafferton, an old woman is dragged from her bed and strangled with a length of flex.

DCS Simon Serrailler and his team search desperately for clues to her murderer. All they know is that the killer will strike again, and will once more leave the same tell-tale signature.

Then they track down a name: Alan Keyes. But Alan Keyes has no birth certificate, no address, no job, no family, no passport, no dental records. Nothing.

Their killer does not exist.