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.

When Fearless Leader uses the monster Humongalon to force everyone to surrender the world to him, Rocky and Bullwinkle try to stop them in the most massive monster battle ever.

In an attempt to reverse Fearless Leader's goop-induced evil powers, Rocky and Bullwinkle travel to an alternate reality to get an "anti-goop."

Rocky and Bullwinkle set out to take away Fearless Leader’s super powers and save the world.