The Treason of the Ghosts (Hugh Corbett Mysteries, Book 12)

In the village of Melford, a local lord is executed for a spate of vicious murders. It's not until the killing begins again, and the dead lord's son alleges that a miscarriage of justice has taken place, that a serious investigation begins. Hugh Corbett realises that for the last five years a serial killer has terrorised the villagers and that when, not if, the next victim is chosen, he must be ready to act.