When Phineas and Ferb think Perry is lost, they use the power of music to find him. Meanwhile, Candace, who fears she is at fault for Perry's disappearance, combs the Tri-State area to find him. As it turns out, Doofenshmirtz has been downgraded to a low-level threat and Perry has been reassigned to a more dangerous villain and a new family. / The Flynn-Fletcher family becomes marooned after a summer storm shipwrecks them on an island, and Phineas, Ferb and Isabella use the opportunity to build a Swiss Family style tree house which angers an already irritated Candace who wants to get back in time for Jeremy's party. Meanwhile, on the same island, Dr. Doofenshmirtz uses free monkey labor to boost a new laundromat business.