Bumblebee wasn't the only one who left Cybertron. An old friend of his followed him to Earth, hiding in plain sight. When Bumblebee met Sam, he did not expect to see her again.
Bumblebee and Optimus have managed to keep a pretty important secret for most of their lives. But when Optimus is held at gun point by Megatron, their secret is finally released. Now it's a race against both time and the truth as Bumblebee is forced to live through his past to determine his future as the son of Optimus Prime and... Megatron.
I do not own Transformers.