An elderly baker named Miller (Ludwig Stossel) is murdered by a sinister stranger (Peter Lorre). A trail leads on to a nightclub singer, Leda Hamilton (Kaaren Verne) who reveals that she and Miller have been in thrall to an organization of Nazi fifth columnists led by Ebbing (Conrad Veidt). She is helped by a well-meaning sports promoter, Alfred "Gloves" Donahue (Humphrey Bogart), who himself is suspected of murdering a nightclub owner (Edward Brophy), and has to track down those responsible to prove his innocence.