A teen-aged high school student (Matthew Broderick) inadvertently nearly starts a nuclear war with the USSR. The young man, a computer geek with a tendency for trouble, breaks into a government computer in order to find new and exciting games to play. What he does not know is that he has hacked into a top secret war planning system, and the intrusion alerts the authorities of his actions. After being chased by the military he sets out to find a reclusive scientist (John Wood) who created a computer that plays games in order to predict future wars. The boy, his girlfriend (Ally Sheedy), and the creator of the computer must convince the military of the real reasons behind the apparent soviet hostilities.