Eager to come face-to-face with a real life monster, Rocky and Bullwinkle buy a creepy old mansion in hopes of finding a real monster.

After Bullwinkle drinks a monster serum, he can't control when he turns into a big hairy monster, so he and Rocky go on the run from angry mobs and internet celebrities.

Bullwinkle and Rocky fly to a mysterious monster-inhabited island to meet the missing mad scientist that created the serum that turned Bullwinkle into a monster, only to learn of the biggest, meanest monster on the island, Humongalon.