Phineas and Ferb accidentally knock an alien spacecraft into their backyard while playing baseball. While they are busy trying to repair it, Candace discovers Meap, an alien she believes is a plush toy that has been "roboticized" by Phineas and Ferb, and sets out to bust her brothers with the evidence in hand. Meanwhile, Phineas, Ferb and Isabella are captured by Mitch, a rogue alien who Meap was tracking before his space craft crashed. Candace and Meap team up to save them while Dr. Doofenshmirtz's battle with Perry lands them right in the middle of the rescue plan.