Phillip Darlington is stabbed to death and Inspector Mallory arrests his son Lawrence after finding a knife in his bedroom; a knife Sergeant Goodfellow saw Mallory plant. Goodfellow after confronting Mallory seeks Father Brown's help who with Sid Carter discover Mallory's wife and children are missing complicating matters. Darlington's daughter, Arabella, also returns home from Oxford having just married that weekend. Brother and sister claim they slept all night; the brother in the house and the sister with her new husband in Oxford. A stolen car and a man, known to Sid's prison contacts, Mallory wronged ten years ago has returned for retribution.