After their gruelling journeys to Galicia and Scilly, Baldwin and Simon are at last back on the English mainland. Eager to get home, they set off on horseback but only get as far as Cardinham on Bodmin Moor. Here, they are detained by the castellan who requires their help to solve two murders on the estate. The first victim is a widow, found dead with her two children. The second is Serlo, the miller, who has recently been discovered embezzling castle money taken in tolls. As Baldwin and Simon begin a double investigation, they must look beneath the village friendships and family loyalties to find an evil killer and secure Cardinham's safety.