After the defeat of evil Doofenshmirtz, there is a new threat in the 2nd Dimension. Phineas, Ferb, Candace, and her resistance fighters must team up to defeat this new foe.

It's been 10 years after the events of the present, and Phineas must decide what university to go to. After discovering that Isabella had a crush on him for years, Phineas must reach her before she leaves for college and express his true feelings for her. Meanwhile, Doofenshmirtz has a mid-life crisis.