Though Henry Fonda is top-billed in The Immortal Sergeant, the title character is played by Thomas Mitchell. Set in the Libyan Desert during WW2, the story finds tough but compassionate British Eighth Army sergeant Kelly (Thomas Mitchell) in charge of a 14-man patrol. Kelly's corporal is Colin Spence (Henry Fonda), a shy and retiring Canadian. When the squad becomes lost in the desert, it is the guidance and example of Kelly that brings the timid Spence out of his shell. Kelly ultimately dies, leaving Spence in charge of the surviving soldiers. Applying the lessons learned from the Immortal Sergeant, Spence is able to lead his comrades back to allied lines, becoming a hero in the process. Second-billed Maureen O'Hara plays Spence's sweetheart in a series of gratuitous but effective flashbacks. Immortal Sergeant was based on the novel by John Brophy.