Hiro discovers a chip for Baymax's creation that was left behind by his late brother Tadashi, which inspires Hiro to recreate Baymax, after thinking his companion was gone forever. Of course, the task isn't as easy or straightforward as it initially seems, and the Big Hero 6 team quickly find themselves in trouble.
Hiro is embarrassed when he learns Karmi is posting fan fiction about Big Hero 6 depicting them as boyfriend and girlfriend. Her imagination comes in handy when she is kidnapped by escaped villain Momakase.