Penn, Boone, and Sashi are zapped back to the super hero world to help Captain Super Captain defeat his twin brother, Professor Evil Professor, who has turned all the superheros evil.

Penn, Sashi, and Boone must travel to the three most dangerous places in the multiverse in order to free Penn's parents as Rippen plans to conquer the Most Dangerous World Imaginable with Larry and those with him after having to close its portal from the other side.