Lovesey, Peter. Peter Diamond mystery.

In a Sussex town on the southeast coast of England, a widely disliked art teacher at a posh private girls' school disappears without explanation. Meanwhile, detective Peter Diamond finds himself in Sussex, much against his wishes. His irritating and often obtuse supervisor, Assistant Chief Constable Georgina Dallymore, has made Diamond accompany her on a Home Office internal investigation. A Sussex detective has been suspended for failing to follow up on DNA evidence that linked a relative to a seven-year-old murder case. As Diamond asks questions, he begins to notice unsettling connections between the seven-year-old murder and the missing art teacher. Could the two cases be connected?