Quick recap
In the 1960s, the Autobot ship Ark crash-lands on the far side of the Moon; in 1969, Apollo 11 secretly investigates it. Three years after Egypt, the Autobots find a piece of the Ark at Chernobyl and recover Sentinel Prime, the former Autobot leader, from the Moon, and Optimus revives him with the Matrix. Sam lives with his new girlfriend, Carly Spencer. Sentinel reveals a deal with Megatron, kills Ironhide and uses the Pillars to bring in hidden Decepticons. The Autobots are exiled from Earth, and the Decepticons take Chicago to pull Cybertron into the Solar System. In the battle, Sam kills Dylan Gould, Carly's boss and a Decepticon ally, and Bumblebee destroys the Control Pillar. Megatron offers a truce, Optimus refuses, tears his head off and executes Sentinel.

