Transformers- The Past comes to the Future

The Autobots are franticly trying to get Bumblebee to some files that the Decepticons are holding. The Decepticons, though, don't want him to find these secret files. All he is told is that he isn't who he seems to be and that it's all hidden in the past. Why did he lose his memories? And why are the Decepticons so fond on keeping it from Bumblebee? All of it is to be told in a story only Bumblebee will understand. Finally, the key to finishing the war will come out.