Decades prior to the start of the film, the American military sponsored a superhero group called "Team Zenith." Its leaders were Jack Shepard, aka Captain Zoom, who possessed super-speed, and his brother, Concussion, who could project sonic blasts. However, the military tried to increase the team's powers by exposing them to an experimental form of radiation called "Gamma-13." This caused Concussion to become more powerful, but it also turned him evil. Concussion killed his teammates Marksman, Ace, and Daravia; Concussion was believed to be killed by Zoom in an explosion (in reality, he had been sent into another dimension). Zoom apparently lost his powers, and retired.
Decades later, the scientist behind the original Zenith Project, Dr. Grant, discovers that Concussion is making his way back into their own dimension. Larraby, the military officer in charge of the Project, decides to form a new Zenith Team to fight him.
Jack finds himself dragged back into the Project, this time as an instructor. He is told that a new team is needed to battle a great menace, but he isn't told what it is. He is told, however, that if natural training does not prepare the new team in time, then they will be exposed to Gamma-13. In their secret base, Area 52 (a reference to Area 51) he meets Marsha, a beautiful but clumsy psychologist, who is a big fan of his, knowing of him only through the comic book propaganda adaptations of the team's adventures.
The project holds an audition of would-be members, most of whom possess useless or disgusting powers. In the end, four young people are selected:
Dylan, a 17-year-old boy who can turn invisible and has clairvoyance
Summer, a 16-year-old girl with telekinetic powers
Tucker, a 12-year-old boy with the power to enlarge any part of his body
Cindy, a 6-year-old girl with super strength.
All of them are shown as having problems adapting to normal life because of their powers