Based on a novel by Leslie Charteris, New York's police commission summons a rogue criminal to eliminate six notorious gangsters that courts cannot convict.
Inspector Henry Fernack (Jonathan Hale) complains that racketeer leaders are not convicted, and the New York police commission sends William Valcross (Frederick Burton) to get Simon Templar (Louis Hayward) from South America. Simon is known as the Saint because his crime victims are criminals. Valcross gives Simon a list of six gangsters in New York. In court charges against Jacob Irbell are dismissed, because no one will testify. Irbell is aiming his gun at someone when he is shot, and Fernack finds Simon's card. Simon climbs in the window of Irbell's lawyer Vincent Nather (Charles Halton), pulls his gun, takes $20,000, and questions him. Fernack comes in and meets Simon, who joins Fernack in his car. Simon asks him about the Big Fella and Papinoff. Cab driver Sebastian Lipke (Cliff Bragdon) thanks Simon for killing Irbell. Simon goes to a poker game and is held by Boots Papinoff (Ben Welden), who asks where he got the money. Papinoff calls Nather and orders Simon taken out of town to Maury Yule. Simon accuses Yule of kidnapping and escapes as Fay Edwards (Kay Sutton) gives him a gun. Simon gets the kidnapped girl and shoots a man before leaving in a car.
Simon sees Fay at the zoo and thanks her, saying that Hutch is next. Hutch Rellin (Sig Ruman) reprimands the doorman and Papinelli. Simon gets in Papinelli's car. Papinelli says he will help Simon get Hutch; but he is shot, and Simon is captured and taken to Hutch. Fay is there. Hymie Fanro (Paul Guilfoyle) and Red Jenks (Jack Carson) drive Simon to Jersey. Simon gets Hymie's gun. Red shoots them both. When Fay arrives, Simon kills Red. She treats Simon's wound at her apartment and says the Big Fella helped her, but she will point him out and kisses Simon. Simon finds two men in his room who question him roughly until Fernack appears. Simon says that he will get the Big Fella, and Fernacks lets him escape with his gun. Simon calls on Hutch and shoots him when he resists. Fay calls Simon to go to a bank. Simon calls cab driver Sebastian and tells Valcross his plans. Valcross shoots Fay, and Simon shoots Valcross, the Big Fella. In the cab Fay dies in Simon's arms. Simon turns wounded Valcross over to Fernack, who sees Simon off to Rio de Janeiro.
Imitating the medieval Templar knights who tried to fight for "good" with violence, the arrogant Simon delights in hunting men he doesn't like. In the fantasy worlds of fiction and movies he can live a charmed life and kill without being killed.