A UFO abducts the Fantastic Four from the Science Centre to Planet X. There, their dictator Kurrgo requests the Fantastic Four save their planet from another planet knocked off its orbit. Reed manages to formulate a working plan to save the population. While the plan is in process, Kurrgo has other ideas. However Reed tricks Kurrgo and leaves him on the exploding planet while the micro-sized population and the Fantastic Four get away to safety.

Dr. Doom challenges the Fantastic Four. Doctor Doom begins his plans by capturing Susan. Soon the Fantastic Four manage to locate and penetrate Dr. Doom's flying fortress, but Ben is turned back to his former self and the other three are trapped. Ben turns himself back into the Thing, releases the others and aborts Dr. Doom's tidal waves. They chase Dr. Doom out and back to the flying fortress. After a struggle through the dangerous complex of the fortress, they abort Dr. Doom's global destruction for good.