A teenage boy named Alex Rogan lives in a trailer park with his mother and younger brother, and dreams of escaping to a better life. He finds solace in playing "Starfighter," an arcade game in which he excels, setting the record high score. One night, after being disappointed for not securing a loan for college, Alex is approached by a man named Centauri, who reveals that the game is actually a training tool designed to find potential starfighter pilots. Centauri whisks Alex away to a space station called the Rylan Star League. There, Alex learns that the game's various space combat scenarios are real and that an intergalactic war against a force called the Ko-Dan Armada is imminent. Alex is expected to join the fight as the last starfighter due to his exceptional gaming skills. However, the anxious and overwhelmed Alex chooses to return to Earth, convinced he is not a hero and cannot make a difference in the conflict.

Back on Earth, Alex discovers that a robotic look-alike called a Beta Unit has been put in his place to cover his absence. As the Beta Unit awkwardly imitates Alex's life, the real Alex faces the normalcy of his existence with a new perspective, realizing the opportunity and responsibility he fled from. Meanwhile, an alien assassin is sent by the enemy to eliminate the last starfighter, leading to an attack that endangers Alex, his family, and his community, compelling him to reconsider his choice.