A pterodactyl-like beast devastates a town and the Superfriends give chase. When even Superman fails to stop it, they realize they have a fight on their hands. Superman determines that the creature is Rokan, a prehistoric monster from his home planet Krypton. To make matters worse, she lay eggs that soon hatch.
Batman and Robin respond when skiers are attacked by strange creatures, in reality baby Rokans that have just hatched. Realizing the world would be destroyed by an entire flock of Rokans, the SuperFriends desperately consult their computer for a solution and it tells them Kryptonite can effect Rokan. However, the amounts necessary to hurt Rokan could kill Superman no matter where in the world he is, even within the lead-shielded Hall of Justice; he tells them to go ahead with the plan regardless.
Wonder Woman and Aquaman leave to find a big enough hunk of Kryptonite while the others battle Rokan and her children. Superman heads to the Hall of Justice to wait things out when they return with the Kryptonite. Rokan flees inside a volcano but they drop the Kryptonite down after her, causing it to erupt and blow the Kryptonite into space. Rokan and her children flee Earth (the episode ignoring how they've only temporarily gotten rid of the monster).