Flash receives a distress call from Prince Barin, summoning him to Mongo to save the planet from Ming's evil son Kro-Tan. Back at Monitor our heroes uncover Ming's plan- Kro-Tan has turned the population of Mongo into slaves who mine the planet of Oceanite, which is turned into slabs and used by Ming to encircle the Earth, thereby blocking out all sunlight and plunging the planet into endless winter. When L.J.'s foolish heroics against attacking robo-ships backfire, the Defenders (sans Flash) counter-attack Ice Station Earth. As Flash and Barin start a slave uprising on Mongo, L.J. is seriously injured at Ming's headquarters, forcing our heroes to surrender. On Mongo Flash and Barin destroy the transporter-computer, breaking apart the oceanite wall and sending it crashing towards Kro-Tan's home planet, while the other Defenders escape from Ming's dungeon and rush back to Monitor to obtain much-needed medical help for L.J.