Young Hiro Hamada is a natural-born inventor and a genius at building robots. Together with his older brother Tadashi, they bring to life the most advanced ideas at the Technical University of the City of the Future, San-Fransokio. After a series of mysterious events, the friends find themselves at the center of a treacherous conspiracy. Despairing, Hiro decides to use the cheerful and good-natured experimental robot Baymax, reprogramming him into an invincible battle machine.