A young bridegroom enlists private investigator William Monk to track down his fiancée, Miriam Gardiner, who disappeared suddenly from a party at a luxurious Bayswater mansion. Monk soon finds the coach in which Miriam fled and, nearby, the murdered body of the coachman, but there is no trace of the young passenger. What strange compulsion could have driven the beautiful widow to abandon the prospect of a loving marriage and financial abundance? Monk and clever nurse Hester Latterly, themselves now newlyweds, desperately pursue the elusive truth—and an unknown killer whose malign brilliance they have scarcely begun to fathom.