Lion-O, Panthro, Tygra, and Pumyra set out to Darkside to free the slaves the Luna-tacks have imprisoned. In doing so, they get captured. Cheetara and Lynxo set out to Sky Tomb to save them. The Thundercats see Mumm-Ra for the first after his ""death"" time at Sky Tomb, and discover that he cannot be harmed by his own reflection anymore. The ancient spirits of evil have made him more powerful when they revived him. They Thundercats manage to escape, and leave the Luna-tacks fighting amongst themselves. (thetvdb.com)