Full story
Reed Richards is a kid genius who, still in grade school, tries to build a teleporter in his garage. He becomes friends with Ben Grimm, a classmate from a poor family, who helps him swipe parts from his relatives' salvage yard. Seven years later, at the high school science fair, the machine makes an object truly vanish, and the demo knocks out the gym's power.
Professor Franklin Storm, head of the Baxter Foundation, sees what he has been looking for: the missing piece for his portal to another dimension. Reed gets a scholarship and joins Franklin's kids, scientist Sue Storm and hotheaded Johnny Storm, plus Victor von Doom, a brilliant, bitter former student who has feelings for Sue. Together they build the quantum gate and send a chimpanzee to a dimension called Planet Zero. It comes back alive.
The government decides the first crewed trip will go to NASA. Fed up, a drunk Reed, Johnny and Victor call Ben and use the machine in secret. Planet Zero is a place of rock and green energy. Victor touches a glowing substance and the ground erupts. He falls and seems to die. Sue pulls the rest back through the gate, but the blast hits them all. Reed stretches like rubber, Sue turns invisible and makes force fields, Johnny bursts into flame and flies, and Ben becomes a giant made of rock.
A year later, the government keeps them locked up and uses Ben and Johnny as weapons. Reed escaped and hid in Central America. Sue helps the military track him down, and he is forced to rebuild the gate in exchange for resources toward a cure. When a team returns to Planet Zero, they find Victor alive, fused to his suit and packing huge telekinetic powers.
Victor, now calling himself Doom, sees Earth as a threat to his world. He kills scientists and soldiers with his mind, goes back to Planet Zero and opens a vortex that starts swallowing Earth. The four follow him. Apart, they get beaten. Together, they turn it around. Ben lands a punch that knocks Doom into the energy beam and he disintegrates. Johnny closes the portal. In return, the government gives them a base of their own to work their way. In the last scene they argue about a team name and Reed suggests the Fantastic Four.