Friend or Foe?

Thaddeus, Thor and their henchmen, offer a truce to Phineas and Ferb, and decide to join them in their activities. While all the neighborhood kids believe them, Phineas and Ferb aren't convinced and believe it is an attempt to spy on them, and sabotage their inventions. Phineas and Ferb infiltrate their house and search for clues to Thaddeus' plan. Is Thaddeus and Thor actually scheming against the boys, or is Phineas just being paranoid?