Gary Cooper is "George Radcliffe" whose testimony at the Old Bailey sends a young, alcoholic "Donald Heath" (Ray McAnally) to jail for murder. Years later, his wife Deborah Kerr ("Martha") receives a letter in the post that was sent at the time, but delayed by a mail robbery, trying to blackmail her husband for the murder. Despite wanting to disbelieve this, she cannot quite dismiss the idea and the more uncertain…