While out on a routine space patrol in the Electro-charger, Mandora encounters an old space freighter which does not meet the inter-galactic standards. She boards the ship for inspection. Finding only its captain on board, she instructs him to land the ship on the Gray Prison Planet for further inspection.Meanwhile, Lion-O and Snarf who had been monitoring Mandora from Cats Lair, recognize the old space freighter as being the Jolly Rogers, the pirate ship of the notorious Captain Cracker. They warn Mandora but Captain Cracker and his robot crew lock Mandora in the control room and begin taking control of the Gray Prison Planet, opening the cells of all the prisoners incarcerated there.Mandora sends the Electro-charger to Lion-O via remote control and he rides it to the Gray Prison Planet. As soon he arrives there, he is attacked by the hulking Rhino, one of the convicts released by Captain Cracker. Luckily, his old acquaintance Quick Pick appears and helps him lock Rhino in one of the prison cells. They then rush off to find Mandora.In another part of the Gray Prison Planet, Captain Cracker has Mandora tied up on top of a giant pot of boiling oil. As he begins lowering her into it, Lion-O and Quick-Pick arrive just in time to save Mandora from being boiled alive. Mandora and Quick-Pick escape but Lion-O gets caught by Captain Cracker and his cronies. They ties him up, blindfold him and make him walk the plank into outer space. Just as Lion-O steps off the plank, Mandora and Quick-Pick catch him in the Electro-charger.Captain Cracker sails his ship to Third Earth with the intention to attack Cats Lair. Lion-O uses the Sword of Omens to summon and warn his friends about the impending danger. The ThunderCats set off in the ThunderTank to intercept the Jolly Rogers as it lands in a nearby river. As soon as Captain Cracker and his robot companions emerge rom their ship,Panthro fires a net from the ThunderTank and succeeds in capturing all of them. Mandora later arrives and takes all the prisoners back to the Gray Prison Planet.