The episode of King of Beasts GoLion used to create this episode of Voltron is titled "Escape from Slave Castle". In that episode the five space explorers return to Earth from a deep space mission. They are horrified to see that during their absence a nuclear war occurred. All of civilization has been destroyed and humanity has been annihilated. As the explorers search the war torn planet they encounter a Galra Empire slave ship. The ship's Captain, Commander Sadak (Yurak in Voltron.) captures the explorers and takes them to Galra's home planet.