When the two Merton brothers are tortured and murdered, there is no shortage of suspects. Principal among these are the Merton sister, the two Douglas brothers, whose family have been feuding with the Mertons for centuries and various inhabitants of the town of Auchenbland, which is controlled by the Mertons, who have suffered from the Mertons' arbitrary decisions. After an arson attack on the Mertons'family home and the torture and murder of the present tenant of the Merton Arms, Detective Sergeant Alistair MacRae is convinced that the former tenant of the inn, who was thrown out by the Mertons about a year previously, is responsible for the crimes. But Detective Chief Inspector Ian Forsyth shoots down his theory and, after a further murder, is able to arrive at the identity of the murderer by the use of some brilliant logical deductions.