After the army shoots down their UFO, the evil Toadmen seek refuge in an underground tunnel and magnetically pull the moon toward earth, causing great disasters. Banner escapes imprisonment, confronts the Toadmen's attack and saves earth.
The Leader, a mutated super villain, learns that Doctor Banner's newest nuclear device is being transported to another military base by a train, and sends one of his Humanoids to attack the train and steal the invention.
The Hulk finally gains control over his body again - but the Avengers are already on his tail. The Space Phantom takes over the bodies of other Avengers.
One by one, the Space Phantom takes over the bodies of the other Avengers. Hulk has to fight one after another. The Space Phanom finally meets his match in the Mighty Thor. Hulk decides that he does not need the Avengers.