The Decepticons have invaded and taken over the Autobots' home planet, Cybertron. The Autobots are determined to fight back and go to Autobot City on Earth for supplies. Decepticons hijack and take over the ship, resulting in a fierce battle between the Autobots and Decepticons, the result of which is devastating. A new threat to the Autobots appears in the form of Unicron, a massive planet-devouring transformer.