Robot 9 (voiced by Elijah Wood) suddenly awakens to find the world around him filled with danger, devastation, and a post-apocalyptic landscape. Carrying a circular object marked with three strange symbols, 9 flees to the streets, where he fortunately encounters the inventor robot 2 (voiced by Martin Landau), who equips him with a voice. However, 2 is tragically captured by a mechanical beast. 9 then finds the veteran 1 (voiced by Christopher Plummer), the mechanic 5 (voiced by John C. Reilly), the eccentric painter 6 (voiced by Crispin Glover), and the strongman 8 (voiced by Fred Tatasciore). 9 and 5 venture out on their own to rescue 2, and in a critical moment, they are saved by the warrior woman 7 (voiced by Jennifer Connelly). Unintentionally, however, 9 reactivates the ultimate mechanical beast. Driven by questions about his origins and his purpose for existence, 9 decides to do whatever it takes to subdue the mechanical beast and save the world...