Millionaire Lord Charlton altered his will in favor of his nephew, Simon Warwick, who had been adopted by American parents when his own were killed in World War II. When Lord Charlton dies, two men claiming to be Simon Warwick turn up in London to claim the estate. Then one is found dead, and Chief Superintendent Henry Tibbett is faced with a double mystery: Who is the murderer—and who is Simon Warwick?