Mumm-Ra creates device that can make Panthro clones. He embeds the spirit of Hammerhand into his clone and sets it free to destroy Third Earth. The Third Earth inhabitants blame the Thundercats for the terror because they think its the real Panthro destroying their villages and burning their crops. The real Panthro finally encounters his clone and, with the help of Lion-O, manages to destroy it. Enraged about his defeat, Hammerhand destroys Mumm-Ra's cloning device.

The Driller, Mumm-Ra's servant who captured Panthro for him in Spitting Image, returns to aid Mumm-Ra once again. His job this time is to drill a hole from the Cats' Lair to the Acid lake, allowing the acid to flow in and eat away at the lair. The Thundercats set out to find the one substance that neutralizes the acid.