The plot of "Transformers: Revenge of the Fallen" follows Sam Witwicky, the human protagonist, as he attempts to enter college. However, he is soon dragged back into the conflict between Autobots and Decepticons, and he allies with Optimus Prime, leader of the Autobots.
"Transformers: Revenge of the Fallen" beings two years after the first film, "Transformers," which concluded with the destruction of Megatron, the leader of the Decepticons. Sam Witwicky, played by Shia LaBeouf, enrolls in college, hoping put the events of the first film behind him. However, Sam is repeatedly attacked by Decepticons on campus, causing him to seek out the aid of Optimus Prime. Sam and Optimus learn that Megatron is still alive and working with the Fallen, a mysterious robot. Sam and Optimus set out to stop them.
In a battle with Megatron, Optimus is killed. Sam and his girlfriend, Mikaela, played by Megan Fox, travel to Egypt to revive him. Sam finds the Matrix of Leadership and uses it to bring Optimus Prime back to life. Newly rejuvenated, Optimus defeats the Fallen in battle, killing him. Vowing vengeance, Megatron manages to escape, along with his second-in-command, Starscream. Sam and Optimus then return to the United States, vowing to continue the fight against the Decepticons.