From Book 1:

She disappeared fifteen years ago. Frank Elder never stopped looking.

Long after Susan Blacklock's disappearance, Detective Inspector Frank Elder has taken early retirement, but the case still plagues his mind – one failure he can never fix.

The prime suspects were jailed for another murder. Now, one of them is on parole – until he vanishes too.

And then the postcards start arriving. Postcards from the killer. Postcards of Elder's daughter...