When a mysterious planet is menacing to collide on Earth, the athlete Flash Gordon (Buster Crabbe) flies by plane to meet his father in New York and stay with him during the collision. While traveling, Flash meets the blonde passenger Dale Arden (Jean Rogers) and they become friends. However, their plane falls, and Flash and Dale jump together using the same parachute. They land nearby the laboratory of Dr. Alexis Zarkov (Frank Shannon), who invites them to join him in a travel in his rocket to the threatening planet in an attempt to avoid the eminent destruction of Earth. When they arrive in the planet, they meet Ming the Merciless (Charles Middleton), the emperor of Planet Mongo, who wants to destroy Earth, and his daughter, Princess Aura (Priscilla Lawson), who has an infatuation for Flash Gordon. The adventure of Flash Gordon in Planet Mongo shows all the characters of the comic strip: he becomes friend of the Prince Thun (James Pierce), the leader of the Lion Men, a people enemy of Ming. He is arrested by the Shark Men in the underwater Shark Palace of King Kala (Duke York Jr.), who is dominated by Ming. Flash Gordon allies to Prince Barin (Richard Alexander), who claims to be the inheritor of the Mongo's throne, and they fight against the Hawk Men, leaded by King Vultan (Jack 'Tiny' Lipson), in the palace in the air, becoming allied in the end. This is the beginning of a magnificent transposition of Alex Raymond's cartoon to the big screen, in a cult movie. The story is divided in thirteen chapters as follows:
1) The Planet of
2) The Tunnel of Horror
3) Captured by Shark Men
4) Battling the Sea Beast
5) The Destroying
6) Flaming Torture
7) Shattering Doom
8) Tournament of Death
9) Fighting the Fire Dragon
10) The Unseen Peril
11) In the Claws of the Tigron
12) Trapped in the Turret
13) Rocketing to Earth