The Mermaids Singing by Val McDermid

Criminal profiler Tony Hill, who has spent years exploring the psyches of madmen. But now he's become one of the hunted...

YOU ALWAYS REMEMBER THE FIRST TIME...
This was the summer he discovered what he wantedat a gruesome museum of criminology far off the beaten track of more timid tourists. Visions of torture inspired his fantasies like a muse. It would prove so terribly fulfilling.

BUT THE NEXT TIME WOULD BE BETTER...
The bodies of four men have been discovered in the town of Bradfield. Enlisted to investigate is criminal psychologist Tony Hill. Even for a seasoned professional, the series of mutilation sex murders is unlike anything he's encountered before. But profiling the psychopath is not beyond him. Hill's own past has made him the perfect man to comprehend the killer's motives. It's also made him the perfect victim.

AND PRACTICE MAKES PERFECT.
A game has begun for the hunter and the hunted. But as Hill confronts his own hidden demons, he must also come face-to-face with an evil so profound he may not have the courageor the powerto stop it...