Optimus prime and Rachet as well as Kapten Lenox investigate Chernobyl facility allegedly has a contact with Decepticon at the ex-nuclear explosion spot. After 40 years being secret, ARK on the moon is finally known by Optimus Prime who found the engine part of Autobot machine warship (ARK). Optimus thought that the ARK has disappeared after cybertron battle.
As the result, Optimus ask about this matter to NASA but he then is disappointed to the human who have been lying on him and keep their secret for life in the earth. Optimus and Rachet come back to the moon and find Sentinel Prime along with 5 pillars on the ARK’s ruins. Then, they get it live back using a matrix on the earth.