Phineas and Ferb get trapped in an alternate dimension where the evil Doofenshmirtz rules the tri-state area. They must find a way back home with the help of their pet platypus named Perry, who they discover is a secret agent.
The Hansen kids are in a jam. Adam and his best friend Duffy have gotten their hands on some tickets for the Headless Horseman concert, and his sister Chelsea has a date with her dreamy boyfriend Peter. The only problem is they're both grounded. Chelsea and Adam will do whatever it takes to get their mom Lynette out of the house, even if it includes a chance meeting with a very mysterious man. Everything seems to go according to plan until their little brother Taylor realizes that this stranger might be a vampire.
Perry's worst fear comes true when Phineas and Ferb finds out that he is in fact Secret Agent P, but that soon pales in comparison during a trip to the 2nd dimension where Perry finds out that Dr. Doofenshmirtz is truly evil and successful.
