In a sensational breach of promise suit, two wealthy social climbers are suing on behalf of their beautiful daughter, Zillah. The defendant is Zillah's alleged fiancé, brilliant young architect Killian Melville, who adamantly declares that he will not, cannot, marry her. Utterly baffled by his client's refusal, Melville's counsel, Sir Oliver Rathbone, turns to his old comrades in crime - investigator William Monk and nurse Hester Latterly. But even as they scout London for clues, the case suddenly and tragically ends. An outcome that no one - except a ruthless murderer - could have foreseen.