Exploring the newly reformed New Thundera, the Thundercats discover that Mumm-Ra is using all the Snarfs as slave labour to dig for the lost Treasure of Thundera.
Mumm-Ra finds the Treasure of Thundera called the Totem of Dera, which has the power to heal and bring inanimate objects to life, and gives it to Vultureman that he might turn it into a device of destruction to use against the Thundercats.
The Mutants arrive and Mumm-Ra has them lure the Thundercats to a strange place where, except for Lion-O, they are all transformed into child versions of themselves.
Jagara cannot work the new Gyroscope alone, so the Thundercats send for someone to aid her. Screwloose, a robot who specializes in the technology, comes to Third Earth. But, Mumm-Ra tampers with his programming, making him destructive.
An ecology inspector comes to New Thundera to inspect the new Cat's Lair. His ship uses the Space Way Airborn Navigation system to direct him to planets throughout the universe. Upon arriving he is ambushed by Two-Time, who steals the ship.
Mumm-Ra retrieves the Sword of Plundarr as the Thundercats arrive on New Thundera. While the Thundercats try to retrieve the sword and treasure, Snarf tries to find a way to free his fellow Snarfs.
Chilla freezes Snarfer's spaceship as he heads back to the Tower of Omens. When Mandora gets involved, Chilla freezes her and becomes a fugitive from the law.
Ravage Island is an island on Third-Earth with a powerful beacon on it that can control minds. Mumm-Ra seeks to use the beacon to make the Thundercats his slaves.