When Phineas, Ferb, and Perry follow Dr. Doofenshmirtz through his "Otherdimensionator", they find themselves in an alternate universe where a second, truly evil Dr. Doof rules over his Tri-state Area with an army of iron-fisted robots. To save his friends from certain doom, Perry makes the ultimate sacrifice by revealing his secret identity as Agent P. Phineas and Ferb escape, meet their 2nd dimension selves, and begin their own mission to rescue Perry.
As they uncover his plot to travel back to their dimension to take over their Tri-State Area, the gang, as well as their alter-egos, must band together to stop him.
So begins an epic battle as our heroes try to save their home from the clutches of Evil Dr. Doof and his sidekick Platyborg. Will Evil Doof succeed and achieve dual world domination? Will Candace finally bust her brothers? Find out in this action-packed, epic adventure—so huge that it crosses over time and space!