Phineas and Ferb are living just one moisture farm over from Luke Skywalker on the planet of Tatooine when R2-D2 and the Death Star plans inadvertently fall into their speeder. With the fate of the galaxy thrust upon their shoulders, they hire pilot Isabella, Han Solo's rival, to help them return the plans to the Rebel Alliance. Complicating matters, low-ranking Stormtrooper Candace is intent on busting the Rebels and chases them across the galaxy in hopes of retrieving the Death Star plans. Meanwhile, intergalactic chaos erupts on the Death Star when Perry the Rebelpus is trapped in carbonite while trying to stop Darthenshmirtz from using his new "Sith-inator." The saga takes a turn for the worse when Ferb is accidentally caught in the crossfire of the "Sith-inator," changing him into a full-fledged Sith and leading to an epic first-time battle between the brothers.