English convicted killer and artist Mervyn Speight, who was found guilty by reason of insanity, escapes from prison. A friend of Mervyn enlists lawyer and amateur detective Hugo Bishop to locate the artist. Bishop’s talent at detective work enables him to locate Mervyn at a London bomb site, the scene of the murder. The escaped convict reveals that he hopes to prove his innocence because he remembers seeing a man’s face before being knocked unconscious and arrested. Meanwhile Mervyn’s wife Thelma, a magazine writer, has been living as the wife of Victor Tasman. Thelma’s editor, Maurice Jerrard, is the only person who knows that her real husband is incarcerated. Since Mervyn’s escape, Thelma fears that he will come after her because of her affair. Bishop comes to believe that Mervyn is sane and innocent, and invites all the other potential suspects to a party. When Mervyn identifies Jerrard as the murderer, Jerrard escapes and, after being pursued by police through London, accidentally falls to his death near the crime scene. Now free, Mervyn travels to Europe so his ex-wife may pursue her romance.