Lion-O takes up mountain climbing, but during one of his climbs, The Mutants attack him with a thundrainium gun, Liono calls the other Thundercats, but an avalanche traps Panthro, Tygra, Slithe and Monkian, in a cave causing a limited air supply. Meanwhile Jackleman steals the sword, but Lion-O manages to get it back and saves everyone.
Elenco: Bob McFadden , Larry Kenney , Earl Hammond , Lynne Lipton , Earle Hyman , Peter Newman , Gerrianne Raphael , Doug Preis , Will Friedle , Emmanuelle Chriqui , Kevin Michael Richardson , Matthew Mercer .