The family takes a short sail trip out to sea, but a storm causes them to wind up stranded on a remote island. To pass the time, Phineas, Ferb, and Isabella, build a set of treehouses with the most modern conveniences, to Candace's dismay, as she wants to get back home in time to attend Jeremy's party. Meanwhile, Perry the Platypus, who was left behind, must get away from the watchful eye of Baljeet and Buford, so he can go on his mission to stop Dr. Doofenshmirtz's latest plot.

To play a game of indoor hide-and-seek Phineas and Ferb shrink down their friends including, their new extreme fan, Irving. Meanwhile, Dr. Doofenshmirtz attaches a nanobot to Perry in an attempt to discover where he lives.