Agent P's fate is finally revealed in the action-packed finale of the two-part television special that left Phineas, Ferb and the gang hanging...literally off an unchartered gorge and Candace frantic over a phone call with Jeremy that left their relationship status in limbo. Now, with Agent P nowhere in sight, Dr. Doofenshmirtz and Major Monogram square off against evil Carl who controls a set of familiar-looking robots to take over the OWCA, in one of the biggest battles yet.

After discovering that a strange planet is hurtling directly towards Danville, Phineas and Ferb set out to avert a disaster, while Buford looks forward to making contact with its alien race. Meanwhile, Dr. Doofenshmirtz hopes to steal the world's largest ball of twine.