The Toxic Avenger must defend his friends from his own evil alternate universe doppelgänger, The Noxious Offender.

When school reporter Roger Smith meets a beautiful subhumanoid named Victoria, they fall in love but becomes determined to save her and the new school from a giant mutant squirrel, Tromie.

Toxie finds he has nothing to do as a superhero, as he has ridden his city of evil. He decides to go to work for a major corporation, which he discovers may be the evilest of all his adversaries.

The Toxic Avenger is tricked into traveling to Tokyo to search for his estranged father, leaving Tromaville open to complete domination by an evil corporation.