Young Ben Crandall (Ethan Hawke) spends his free time watching sci-fi films, playing video games and reading comic books. Surprisingly, his affinity for all things fantastical yields a real result — when he has a vivid dream about technology, his science-loving friend Wolfgang Muller (River Phoenix) manages to create a working spacecraft. Joined by their buddy Darren Woods (Jason Presson), the boys take off into outer space and encounter some very odd extraterrestrial life.
High school student David Lightman (Matthew Broderick) unwittingly hacks into a military supercomputer while searching for new video games. After starting a game of Global Thermonuclear War, Lightman leads the supercomputer to activate the nation’s nuclear arsenal in response to his simulated threat as the Soviet Union. Once the clueless hacker comes to his senses, Lightman, with help from his girlfriend (Ally Sheedy), must find a way to alert the authorities to stop the onset of World War III.