It's been almost half a year since Summer ended and Phineas is already bored with school and misses his summer adventures with his step-brother Ferb, as well as his pet platypus Perry misses his days as a secret agent for the OWCA. When Spring Break starts, Phineas and Ferb discovers that Perry's former nemesis Heinz Doofenshmirtz has funded the construction of a Phineas and Ferb Memorial Museum, complete with exhibits of their summer inventions. Phineas, Ferb, their sister Candace, and Phineas' girlfriend Isabella, go to see the grand opening of the museum, and reminence about their fun-filled summer adventures. Meanwhile, Perry is called to an OWCA reunion along with Doofenshmirtz, together they converse about their past battles.