The Lunatacs hook up exercise machines to generate power for Sky Tomb's engines, but their own laziness forces them to find Thundercats to do the hard work. Meanwhile, Mumm-Ra plans to lure the Thundercats into a freezing trap in the Caverns of Cold on New Thundera.

The Thunderscope

Lion-O and Snarf recover a mysterious telescope from the wreckage of their original spaceship. Mumm-Ra recognizes it as the Thunderscope, which allows its user to locate pieces of the Treasure of Thundera. Lion-O must discover its purpose and keep it out of Mumm-Ra's evil hands.

The Jade Dragon

Mumm-Ra discovers the power of one of the pieces of the treasure of Thundera. The Double-Headed Dragon of Doom, or the Jade Dragon possess the power to entrap people in its stomach. The legend says that Haji-Man's ancestor gave the dragon to his wife as a marriage gift, and since her father was so against their marriage, he put a curse on the dragon and it engulfed Haji-man's ancestor. Jaga freed the him, and he gave the dragon to Jaga for safe keeping. Now, the Thundercats have found the Jade Dragon, and Mumm-Ra manages to trap Lion-O and Cheetara in it. Haji-man is their only hope.

The Circus Train

A bounty hunter known as Captain Bragg comes to Third Earth to help the Thundercats get rid of the Mutants and the Lunatacks. Capt Bragg tricks Wilykat in going with him and they first go after the Mutants. After capturing them, they go to capture the Lunataks. They capture all except Luna and Amuk, who free the other Lunataks, put Bragg in a cage and tie Wilykat to the train's engine.

The Last Day

Impatient with Mumm-Ra failing them time and time again, the Ancient Spirits of Evil give him one final chance: destroy the Thundercats within twenty-four hours, or face exile. To this end, he is granted extraordinary power by the Spirits, and grows to a gigantic size.