It is the day of reckoning. The Autobots, led by Optimus Prime, make a perilous last stand to hold off the Decepticon conquest of Cybertron. Outnumbered, outgunned, and pushed to the brink of extinction, the battle-weary band of resistance fighters orchestrates a desperate series of counterstrikes on a mission that, if everything somehow goes right, will end with an unthinkable choice: kill their planet in order to save it.