Private detective Simon Templar, known as "The Saint," becomes entangled in an investigation of a major San Franciscan crime ring headed by an elusive character known only to the police as Waldeman. When a gang murder occurs at the Colony Club on New Year's Eve, it triggers the flight of Val Travers, the daughter of a police inspector who committed suicide after his humiliating discharge on suspicion of being a member of Waldeman's gang. Val, who has organized a gang of second-rate hoodlums to ferret out the mysterious Waldeman and thus exonerate her father, runs into Templar as she tries to elude the police. When the San Francisco police department sends for Inspector Henry Fernack of the New York City police department to help with their investigation, Fernack forms an uneasy alliance with Templar. At police headquarters, Templar hypothesizes that Travers was framed by an inside man at the police department, but his theory is ridiculed by criminologist Cullis, who suggests that Templar is Waldeman. Learning that the murdered man was to have met Martin Eastman, a well-known philanthropist, Templar breaks into Eastman's safe, where he finds a stack of federal bank notes that have been stolen by Waldeman's gang. When Eastman fails to report the robbery but visits Cullis instead, Templar suspects that Cullis and Eastman are in league with Waldeman, but the police are unable to arrest them for fear of losing Waldeman. To flush out Waldeman, Val and Templar visit Eastman's house, where Templar has secretly returned the bank notes. Faced with the stolen notes, Eastman panics and runs from the house, where he is shot. Templar and Val next pay a visit to Cullis and confront him with the incriminating notes, forcing him to confess that he framed Val's father. Unknown to Cullis, the police have installed a dictaphone in his office and are listening to his confession. When Cullis accuses Templar of being Waldeman, the police commissioner announces that Templar has been working with the police from the begininng, and Cullis finally admits that Allen Breck, Val's meek legal advisor, is the elusive Waldeman.