School is out for summer, and stepbrothers Phineas and Ferb have decided to make each day an adventure! Their inventions end up causing trouble for their sister, Candace, who can get their mother to see the evidence of their creations. Meanwhile, the family's pet platypus leads a double life as secret Agent P and faces off with the evil Dr. Doofenshmirtz, who is trying to take over the Tri-State Area.