The chemical HOS92, a product of the Choate Chemical Plant, is inadvertently dumped into a swamp. It creates a Swamp Monster that obeys its orders from a mysterious entity to obtain more of the life-giving substance. After the creature attacked Dr. Diablo, Ellis Johnson calls the Ghostbusters and tells them about the situation. While the Ghostbusters investigate, Dr. Diablo attempts to get rid of the HOS92 reisude with a new product called GSMT. However, this instead results in creating a new race of purple Swamp Monsters. After a battle between the green and purple monsters, the Swamp Creature reveals itself and explains that the monsters and itself are a hive mind and that only want to survive. They then take all of the remaining barrels of HOS92. After the Ghostbusters leave the scene,