Demoted FBI agent Art Jeffries (Bruce Willis) embarks on an almost hopeless battle against ruthless security agents to protect Simon Lynch (Miko Hughes), a 9-year-old autistic boy who happened to crack the top-secret and "absolutely safe" U.S. military code "Mercury." This makes the million-dollar code vulnerable, especially if enemies of the United States learn of Simon's abilities and make him their hostage. The head of the special unit, Nick Kudrow (Alec Baldwin), orders this threat to national security to be eliminated immediately. But Jeffries thwarts his plans. Pursued by killers, Jeffries realizes that he can't trust anyone. In a desperate race against time, there is only one chance of survival: he must use Simon's special abilities against the enemies in order to bring them to justice.