Christmas looks bleak for Superintendent Runcorn of the Metropolitan Police. Hoping that a change of scenery will free him of thoughts of Melisande, the woman who stole his heart, Runcorn heads for the Isle of Anglesey. But his plans are ruined when he discovers that Melisande is also in Anglesey and, moreover, that she is engaged to another man. When the local vicar's sister is discovered murdered and Melisande's brother is implicated in the crime, Melisande turns to her old friend Runcorn for help to clear her brother's name. Determined to assist Melisande in her time of need, Runcorn resolves to find the killer.