When Rex Graves holds a housewarming party in the Scottish Highlands, he doesn't anticipate the arrival of an old flame—much less a dead body or serial killer. Rex's houseguest and colleague Alistair, who recently made an unsuccessful attempt to convict a man for the notorious Moor Murders, now finds himself under the same roof as the killer. Rex must use his skills of intellect, observation, and logic to save Alistair's career and bring the murderer to justice.