Confined to a mental institution for killing his wife, Alex Forrester (Stuart Whitman) learns from his doctor (Edward Mulhare) of an arcane law that guarantees escaped patients new trials. Believing he's no longer insane, Alex breaks out of the asylum and hides in the home of Molly Thomas (Joanne Woodward), a married woman who lives nearby. So when her husband's body is found in the woods and the police assume he's the killer, Alex must find a way to prove he's sane and innocent of the murder. An ingenious thriller packed with clever twists and turns, Signpost to Murder is based on the 1962 London stage play by Monte Doyle, which ran 419 performances and starred Margaret Lockwood as Molly.