After being captured, Starscream is given a final chance at being allowed in the Decepticons. That is, if he can survive a trip with a new prototype machine created by Soundwave called the Trans-Dimensional Warp cannon. Which transports him to Equestria, now all he has to do is return home. With the help of some new (and old) 'friends', what could possibly go wrong? It's only Starscream.
(Potential Spoilers. This is set before Breakdown is killed and before Starscream has the Apex Armor or loses his T-cog).