Dispensation of Death (Medieval West Country Series #23) by Michael Jecks
1325: England is a hotbed of paranoia under the reign of the increasingly unpredictable Edward II and his lover, Sir Hugh le Despenser. When the Queen's lady-in-waiting is slaughtered and a man's body, hideously mutilated, is discovered behind the throne, the King demands to be avenged. Sir Baldwin de Furnshill, an experienced investigator of murders, is appointed to track down the killer, aided by his friend, Simon Puttock. In an age of corruption, when the king's friends can use torture, blackmail and murder to promote their ends, a rural knight and bailiff must fight to stay alive.