A shadowy figure fires a flare out of a window. The flare forms the words "The Fantastic Four!"

Susan Storm is having tea with a friend. When she sees the flare, she turns invisible, gets into a cab, and offers the surprised driver a banknote when she reaches her destination.

Ben Grimm is trying to find a coat that fits him. A clerk in the haberdashery sees the flare. Grimm bursts out of the too-small door, rips a manhole out of the street, follows the sewers, and bursts out when he thinks he has reached his destination.

Johnny Storm is working on his latest hot rod in a service station. The mechanic sees the flare, which turns into the number 4. Johnny bursts into flame and flies away, destroying his car. The authorities treat him as an enemy attack, so he reluctantly melts the jets that come after him. A nuclear heat-seeking missile locks onto him, and just as Johnny's flame starts to fade, an impossibly long pair of arms grabs the missile and throws it out to sea.

Johnny's saviour is the same man who fired the flare. He greets Susan, Ben, and Johnny with the words, "There is a task that awaits us ... a fearful task!" But how did these four people become so fantastic?

To beat the Communists into space, scientist Reed Richards, sister and brother Sue and Johnny Storm, and pilot Ben Grimm sneak off into space in a rocket. In space, the four are bombarded by cosmic rays. The auto-pilot lands the ship back on Earth, where they find themselves physically transformed and possessing remarkable new abilities. Sue can turn invisible. Ben has transformed into an orange, muscular "thing." Reed's body became highly malleable, allowing him to stretch into any shape. Johnny's body bursts into flame, and he can fly. They decide to use their abilities to become the super-team known as the Fantastic Four. They give themselves the individual names Mr. Fantastic, Invisible Girl, Human Torch, and the Thing.
(Chapter 2) The Fantastic Four Meet the Mole Man!
Atomic plants in the Soviet Union, Australia, and South America have been mysteriously attacked by cave-ins. Another attack occurs in Africa, where a huge monster burrows out of the ground but is recalled by a human figure. The Fantastic Four travel aboard their private jet to Monster Isle, which Reed has deduced is the same distance from each attack. There, they are attacked by a giant three-headed monster. Reed stops the monster, but a cave-in separates Reed and Johnny from Ben and Sue. Beneath the island Reed and Johnny land in the Valley of Diamonds, which temporarily blinds them. The Mole Man appears, revealing he is responsible for the attacks.
(Chapter 3) The Mole Man's Secret!
The Mole Man explains his origin. Having been ridiculed by humanity, he went off alone in search of the legendary land at the centre of the earth. Eventually he washed ashore on Monster Isle. Making his way through a cavern, he was caught in an avalanche and rendered almost blind. However, due to his other heightened senses taking over, he mastered the subterranean creatures and built himself an underground empire.
Meanwhile, on the surface, Ben wrestles a rock monster. Ben and Sue find their teammates listening to the Mole Man's plan to invade the surface world. He sends his monster army against the Fantastic Four. Whilst Johnny distracts the biggest one, the team flees through a tunnel, which Johnny seals shut behind them. After the Fantastic Four escape in their jet, Mole Man destroys the island so the surface world cannot trouble him again.

---