The trio is transported onto a space ship whose human occupants are set to arrive on a new planet to colonize. However, Penn finds himself in the form of a mouse and must save the ship from a feline Rippen who seeks to plunge it into a black hole.

A return to the Knight World causes issues for Boone when he meets a better wizard than himself.

Boone gets a bad report card from Phyllis, making his parents mad. He tries to fix this while on a mission in the Giant Monster World.

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.