It's a typical day on Third Earth — the Mutants set a trap for the Thundercats by attacking a traveling tabbot, Tygra and Cheetara get captured while answering the cries for help, the other Thundercats show up as expected to save them, Thundercats fight Mutants, Thundercats win thanks to the Thundertank, Mutants retreat humiliated back to Castle Plun-darr.
It's not fair! The Thundercats have all this technology and equipment they can use in battle, but the Mutants lost everything when Mumm-Ra sank their ship. Surely that's the only reason the Mutants keep losing, right? Right! If they had access to their own technology, it would tip the scales in their favor, right...? Slythe's certainly able to get Mumm-Ra to think so. He convinces the mummy to raise the spaceship he buried in the quicksand, arguing it's the only way they'll be able to defeat the Thundercats and restore Mumm-Ra's uncontested reign over Third Earth.
As Slythe asks, Mumm-Ra returns the Mutants' ship to them. Hurray, now they have a giant, powerless, rusting, broken lump of metal! It turns out, sitting under quicksand for months doesn't leave your machine in very good condition. The ship itself is useless, but it's not a total loss. The equipment on board mostly still works, including several vehicles. They'll transfer all working equipment to Castle Plun-darr and put three of the vehicles to work right away.
Back at Cats Lair, the Thundercats are surprised to find themselves being ambushed by Mutants in flying and land vehicles. Panthro and Lion-O pursue the latter in the Thundertank. Slythe leads them on a chase through the trees and into the river. No problem — the Thundertank can travel underwater easily... but not on its back, which is how it lands, right over a chasm. Panthro and Lion-O get out easily using Panthro's breathing equipment, but they can't get the Thundertank free. Its doubly important they get it out because it's trapped a baby Sea Quine (a giant seahorse) in a cave in the wall. Fortunately, Lion-O's able to hook Slythe's Nose Diver, forcing the Mutant to pull it free.
Back on the surface, Tygra takes out Jackalman's Sky Cutter, and Wilykit takes out Monkian's using a trap involving a tar pit and a Tree Buchet. The Thundercats reunite, victorious but apprehensive about how the scales have tipped in their war with the Mutants.
This episode provides examples of:
- After Action Patch Up: Mild version.Tygra: Ouch!Cheetara: Sorry, Tygra — the adhesive stuff from the Mutants' net takes forever to remove.
- Amphibious Automobile: The Nose Diver operates both on land and underwater.
- Crazy-Prepared: Of course Panthro has underwater breathing equipment in the Thundertank. As he said, "The time to prepare for a rainy day is when the sun is shining."
- Flying Car: The Sky Cutters can also be driven on land.
- Inescapable Net: Extra points because when Lion-O sees Cheetara and Tygra caught in it, he immediately thinks it doesn't make sense because they should have been able to escape easily. It's partially justified by making the net sticky like a spiderweb.
- Nice Job Fixing It, Villain: Slythe returning to finish off Lion-O and Oanthro allows them to use the Nose Diver to pull the Thundertank free.
- Seahorse Steed: The Sea Quines are seahorses big enough for Lion-O and Panthro to ride while trying to pull the Thundertank free.
- Smart Ball: Slythe picks it up in this episode. He's caught on to the fact that the Thundercats always know when one of their own is in danger, and he's noticed that Mumm-Ra isn't as omnipotent as he claims, deducing that he can't leave his pyramid for very long without losing all his power.
- Trapped in a Sinking Car: Variation — the problem isn't that the Thundertank's underwater but that it's been flipped upside down underwater.
