Plot
Dr. Reed Richards, along with his friend, Ben Grimm, convinces Dr. Victor von Doom, CEO of Von Doom Industries, to allow him access to his space station to test the effects of exposure to clouds of cosmic energy on biological samples. Victor agrees and recruits his chief genetics researcher (and Reed's ex-girlfriend) Susan Storm and her reckless brother Johnny Storm.
They arrive in space to study the cosmic clouds, but the clouds arrive ahead of schedule. Reed, Susan, and Johnny leave the shielded station to rescue Ben, who is out on a spacewalk to place the samples, while Victor closes the shields behind them to protect himself. The storm breaks through the station and strikes the four. They return home but soon begin to develop strange powers. Reed can stretch like rubber, Susan can become invisible and create force fields, Johnny can engulf himself in fire, and Ben becomes a large, rock-based creature with superhuman strength and durability. Victor, meanwhile, faces backlash from his stockholders over publicity surrounding the failed mission.
On the Brooklyn Bridge, Ben accidentally causes a traffic pile-up while stopping a man from committing suicide. The four use their powers to contain the damage and save lives. While the public cheers them for their efforts, Debbie (Ben's fiancée) arrives to silently end their engagement, unable to accept him for his condition. Reed vows to a heartbroken Ben to reverse the effects. The media dubs them "The Fantastic Four," and Victor exploits the news story to his stockholders, but they decide to pull out of Von Doom Industries. The four move into Reed's lab in the Baxter Building to study their abilities and work on finding a cure. Victor offers his support in their efforts but blames Reed for the mission's failure.
Reed plans to construct a machine to re-create the storm and reverse their conditions. However, Johnny refuses to cooperate, insisting they should just embrace their powers. Meanwhile, Victor, also affected by the storm due to the shields' malfunction, begins mutating into organic metal capable of producing electricity, and plots to use his new powers to take revenge.
Victor drives a wedge between Ben and Reed, prompting Ben to walk out in a rage. This motivates Reed to attempt the machine on himself, but he cannot generate enough power to push the storm to critical mass. Victor hears this and brings Ben to the lab. Ben is placed in the machine, and Victor uses his abilities to produce the electricity needed to power it, turning Ben back to normal and accelerating Victor's condition, causing much of his body to turn to metal. Victor knocks the human Ben unconscious and kidnaps Reed.
Victor, now calling himself "Doom," tortures Reed using a super-cooling unit and fires a heat-seeking missile at the Baxter Building to kill Johnny. He flies through the city to evade it, lighting a garbage barge on fire to trick it. Sue rushes to free Reed and battles Doom, but is outmatched. Ben arrives to help, having transformed himself back into The Thing by reusing the machine. The battle spills into the streets, and the four assemble to battle Doom. Johnny and Sue combine their powers to wrap Doom in an inferno of intense flames, and Ben and Reed douse him with cold water, inducing thermal shock and freezing Doom in place.
In an epilogue, Ben tells Reed to forget about his experiment with the machine, as he has accepted his condition through his relationship with Alicia Masters, a blind artist. The team decides to embrace their roles as superheroes, and Reed proposes to Sue. Meanwhile, a frozen Doom is transported back to his homeland of Latveria.