The guys believe Perry is lost and try to find him, not knowing he has been reassigned to track a new villain after Doofenshmirtz is downgraded to a low-level threat.

After becoming marooned on an island after a storm, Phineas and Ferb build an elaborate island tree house as a shelter. Meanwhile in a inactive volcano on the island, Dr. Doofenshmirtz enslaves monkeys to help him start a laundry cleaning business so he can eventually replace all the laundromats in the Tri-State Area with a franchise of "Evilology" institutes.