After successfully repelling Mumm-Ra's all-out attack on the Cat's Lair with the help of Calica and her new android allies, the ThunderCats are left with a single burning question: Where is Lion-0? The answer to that mystery is finally revealed here, as the brash young leader escapes from Mumm-Ra's captivity with the help of a mysterious robed stranger only to find himself alone on an alien world, fighting for his life!