Eight-year-old Mike Hillary, Marc Donato, dreams of fire as a blaze erupts in his room, and his mother, Carmelina Lamanna, dies trying to save him. He ends up at the home of his grandparents, Grandpa Vern and Grandma June, with Dennis O'Connor and Jennifer Higgin, where his duvet smolders and he slips into a drawn bath to sleep.
Now 24, Mike Hillary, an unemployed minor-league baseball player, still sleeps in that drawn bath. After reading a short note from an old friend of his mother, which reads, > "I believe you," he drives to her hometown to confront town sheriff David Nerman Masterson, who suggests considering the athletic counselor job at the community centre. Mike asks why his mother left; Masterson explains she was pregnant and unmarried, but offers no more answers. Frustrated and angry, Mike leaves just as a fire starts in Masterson's trash can.
Mike begins work at the community centre. He notices children painting the number 11 surrounded by flames on a wall, and James, Jared Durand, is the only one who fears the water. Mike seems to give the boy an emotional boost, much to the delight of Jessica Randall, Ingrid Kavelaars, the instructor. Later, she catches up with him while jogging. They are accosted by her bully ex-boyfriend, Blaine, Mark Lutz, and a fight ensues, with Mike manifesting a powerful pyrokinetic touch that ignites objects and leaves Blaine with burns on his chest.
During a baseball game at the community centre, Mike has a vision of James being hurt and bullied by Bart, Kevin Zegers. He finds them and stops it. Meanwhile, at the sheriff's office, Blaine claims Mike attacked him and has "superhuman powers." Masterson remains skeptical—until Blaine shows a hand-shaped burn on his chest. Later, Mike swims in the community centre pool with Jessica, who notices the water getting warmer. At her apartment, he opens up, they share a kiss, and another fire starts. Mike extinguishes it with his hands, which remain unburned. Jessica now knows his secret. He warns her to keep away and runs off.
Two successive nights bring two powerful-looking men emerging from a lake—aliens in camouflage biosuits—the bounty hunter Eleven, Douglas O'Keeffe, and Sixty-six, Andrew Jackson.
Masterson eventually reveals what his knowledge about Mike's mother was: she believed she had been impregnated by an alien and left town before Mike was born. Mike is horrified, a lamp bursts into flames, and he orders Masterson to leave. That night, Blaine sneaks into Mike's motel room and Eleven kills him when he learns of Mike's connection to Jessica.
The next day, Eleven goes to interrogate Jessica at the community centre, while James repeatedly chants "Eleven." Mike, aided by extrasensory perception and precognitive visions, sees through the danger and rushes to help. Jessica flees, and Eleven corners her with a wall of fire. Mike arrives, calling for her, and dives in, only to be ambushed by Eleven. Sixty-six intervenes to save Mike and subdues Eleven with a burst of flames.
Mike awakens in a car driven by Sixty-six, who explains that experiments on humans and other terrestrial life have occurred for thousands of years, and that Mike is a mere "viable specimen"—but Sixty-six refuses to let anything happen to him. The car bursts into flames and Mike runs into the woods. A fiery duel between Eleven and Sixty-six ends with Eleven vanquished; Sixty-six, wounded by Earth's atmosphere, leaves Mike with unanswered questions. Mike sets his body adrift and ignites it.
Mike and Jessica leave town together, with she offering to take precautions and producing a fire extinguisher. Back at the community centre, Bart bullies James again, and a fire is discovered in James's hall locker.
