While taking a special tour across the new pripara's around the world inside of the Prism Train, an accident occurs hurtling them off into a new dimension entirely! There, not only are the girls trapped in a world of horses, but they become them as well! How will our idols ever escape!? How will they get back to their adoring fans?! And will they even want to after learning that these horses don't have any idols to speak of!?