After they lose a fierce civil war to their enemies, the Decepticons, Optimus Prime and his Autobots must regroup to fight another day. Fleeing their fallen home planet of Cybertron, Optimus Prime sends a young scout, B-127, to Earth and orders him to wait for their arrival. When he crash-lands in the middle of a training exercise carried out by a secret government agency, they attempt to neutralize him, but B-127 escapes. Taking on the temporary form of a battered Volkswagen Beetle, he is gifted to teenager Charlie as a present on her 18th birthday, who soon discovers shes received much more than she bargained for. As they strike up a friendship which helps Charlie navigate her ongoing grief after the death of her father, she and Bumblebee must evade the authorities and the pursuing Decepticons in this unexpectedly poignant prequel from the Transformers franchise.