The Autobots investigate the return of the Decepticons and must account for a group of young humans who become involved in their eons-old conflict.
The Autobots go in search of Cliffjumper, whose life signal is weak and find Megatron wielding the dangerous Dark Energon.
The Decepticons, in order to find the Autobot base, capture and torture Secret Agent Fowler, and it's up to Bulkhead and the three human kids to track him down. Meanwhile, Megatron raises an army of undead Transformers.
The kids, along with Bulkhead, Arcee and Bumblebee storm the Decepticon ship to rescue Agent Fowler, and come across the blueprints for a secret plan. During this, Optimus Prime and Ratchet fight against Megatron's army of undead Transformers.
Through his Space Bridge, Megatron raises the dead Transformers of Cybertron, and summons them to Earth. The Autobots have to find a way to sabotage the Bridge, or else their new home will be destroyed by the legion of undead Decepticons.
The Autobots capture Soundwave while Megatron decides to resurrect a former plan.
While Optimus faces off with Predaking, Megatron mounts a campaign to form a new alliance with Rachet.
Ratchet finds himself in a series of predicaments as he resumes his experiments on Synthetic Energon.
The fate of Earth hangs in the balance as the Autobots and Decepticons march toward their last stand.
