MUMM-RA has a phial of miniaturization gas. VULTUREMAN builds a mechanical WOLFRAT to infiltrate the gas into the Cats' Lair. The THUNDERCATS are immediately reduced to nine inches high. Knowing how vulnerable the THUNDERCATS are in this state, MUMM-RA orchestrates a MUTANT attack on the Cats' Lair. The THUNDERCATS' only hope is SNARF; they armor SNARF and use him as a battle charger while TYGRA works on an antidote. The THUNDERCATS finally take the antidote, and SNARF, getting an accidental whiff of it, grows to huge proportions. In his gigantic state, SNARF terrifies the MUTANTS and puts them to flight.

An evil robot monster is attacking the Tuska Village, in an area unexplored by the Thundercats. Turmagar, the leader of the Tuskas, travels to the Cat's Lair to ask for aid in defeating the Techno-Pede robot which is destroying his village. The Thundercats agree to help Turmagar, and set out to the Tuska Village.

Willa is practicing her long-bow skills when a warning device alerts her to a Mutant attack. Willa is captured and the ThunderCats rush to rescue her.

Vultureman invents a Super Power Potion which give him magical powers, enabling him to mesmerize and defeat Tygra.

Mumm-Ra uses the Beacon of Ravage Island to make the Thundercats his slaves. When the beacon puts Lion-O, Panthro, Cheetara, and Pumyra under its power, they are easily captured by the Mutants, and Snarf must get the others at the tower for help, but Ben-Gali soon falls under the beacon's power and it's up to Lynx-O, Snarf and Snarfer, to save the "enslaved" Thundercats.

With only Lion-O and Snarf guarding the Lair, Mumm-Ra decides this is a perfect opportunity to invade the Lair, so Ma-Mutt captures Snarf and Mumm-Ra switches Snarf and Ma-Mutt. Ma-Mutt (who now looks like Snarf) goes to Cats Lair and gives Lion-O some poisoned candy fruit. Lion-O becomes ill and realizes that this Snarf is really Ma-Mutt and Mumm-Ra arrives and defeats Lion-O. Snarfer's bad dream of Snarf becoming a dog causes him, Ben-Gali, and Pumyra to go to Cats Lair, but Mumm-Ra lays a trap for them. He sends Ma-Mutt to get Snarfer and Lion-O becomes better again and distracts Mumm-Ra. When Lion-O summons the other Thundercats, Snarf (who looks like Ma-Mutt now), using Mumm-Ra's chant that changes Mumm-Ra into the everliving, becomes... Snarf-Ra the everliving and he rescues Ben-Gali, Pumyra and they in turn rescue Snarfer from Ma-Mutt. Then Snarf-Ra challenges Mumm-Ra and defeats him. After the battle is over, Lion-O uses the sword to restore Snarf to his original state.

Tygra, on a solo trip to New Thundera to meet the other Thundercats, decides to take a shortcut through a meteor shower. His ship is damaged, and he lands on an unexplored region of New Thundera. The Moss-Land. It turns out that the moss in moss-land is part of a giant monster who captures Tygra with its moss. Lion-O and Panthro set out to save Tygra and battle the Moss Monster.