Siege of Red River stars Van Johnson as a Confederate officer, who "appropriates" a shipment of gatling guns from the Northern troops in the waning days of the Civil War. Posing as a medicine show entrepreneur, Johnson smuggles the guns through enemy lines in his wagon. Renegade rebel Richard Boone steals the guns in order to sell them to the Indians. Surrendering himself to Union troops, Johnson sets after Boone with Yankee reinforcements in tow before the Indians can get their hands on the weapons. After Boone is killed, a northern nurse (Joanne Dru) pleads eloquently for the Yanks to be easy on Johnson; he is allowed to escape, but not before promising to marry the nurse at war's end.