Episodes 1-5
The Planet of Peril
The planet Mongo is on a collision course with Earth. Dr. Alexis Zarkov takes off in a rocket ship to Mongo, with Flash Gordon and Dale Arden as his assistants. They find that the planet is ruled by the cruel Emperor Ming, who lusts after Dale and sends Flash to fight in the arena. Ming's daughter, Princess Aura, tries to spare Flash's life.

The Tunnel of Terror
Aura helps Flash to escape as Zarkov is put to work in Ming's laboratory and Dale is prepared for her wedding to Ming. Flash meets Prince Thun, leader of the Lion Men, and the pair return to the palace to rescue Dale.

Captured by Shark Men
Flash stops the wedding ceremony, but he and Dale are captured by King Kala, ruler of the Shark Men and a loyal follower of Ming. At Ming's order, Kala forces Flash to fight with a giant octosak in a chamber filling with water.

Battling the Sea Beast
Aura and Thun rescue Flash from the octosak. Trying to keep Flash away from Dale, Aura destroys the mechanisms that regulate the underwater city.

The Destroying Ray
Flash, Dale, Aura and Thun escape from the underwater city, but are captured by King Vultan and the Hawkmen. Dr. Zarkov befriends Prince Barin, and they race to the rescue.