When the entire population of Earth suddenly turns violently on the Fantastic Four, the team has nowhere to run until a strange robotic visitor offers them asylum on another planet. Though they suspect a trick, the team agrees, traveling to the mysterious Planet X, where things take an even worse turn for our heroes.

Kuurgo, leader of the people of Planet X, has lured the Fantastic Four to the planet for one purpose: to force them to save Planet X from an impending collision with a rogue planet.

It's up to Mr. Fantastic to devise a way to rescue an entire world, or else he, his team, and the inhabitants of Planet X will perish forever.

In the end, they manage to make the inhabitants of Planet X shrink down to a tiny size, so that they will all fit into one ship. The Fantastic Four then get permission to leave, and do so.