The Pure in Heart by Susan Hill

DCI Simon Serrailler comes home to the cathedral town of Lafferton from Venice because his severely handicapped younger sister Martha is near death. The Serrailler family are divided about Martha's quality of life since she can't speak and has the mind of a baby. Soon after returning, David Angus, a local boy, goes missing while waiting for a ride to school. Besides his sister, David's disappearance is Simon's top priority. It doesn't help that he's being stalked by women he was once involved with. Aided by DS Nathan Coates, he struggles to find out what happened to the boy. Susan Hill writes another fantastic police procedural with a twist. I wrote about the first book in the series, The Various Haunts of Men earlier this month.