Sam Witwicky (Shia Labeouf) is forced to take on the Decepticons in a battle to save a spark that is so powerful it can be used to destroy the world. These Decepticons are now lead by the fallen, Megatron, who has come back to help take over this spark. Sam and Mikaela (Megan Fox) must get help from the Special Forces that work together with the Autobots to protect the planet. Together they must keep the last prime from falling so that Earth can be saved. The battle takes Sam and Mikaela back into the history of the Autobots as they learn how they got here, why they were here, and what happened to create such a degree of violence between the two races.