The Sleeping and the Dead by Ann Cleeves
A diving instructor makes a gruesome discovery in Cranwell Lake - the body of a teenager who has clearly been in the water for many years. Detective Peter Porteous is called to the scene. After trailing through the missing persons files, he deduces that the corpse is Michael Grey, an enigmatic and secretive young man who was reported missing by his foster parents in 1972.
As the police investigation gets under way in Cranwell, on the other side of the country prison officer Hannah Morton is about to get the shock of her life. For Michael was her boyfriend, and she was with him the night he disappeared. The news report that a body has been found brings back dreaded and long buried memories from her past . . .
'Cleeves again excels in her sense of place in this cleverly plotted psychological thriller' The Times