Primitive cave-aliens who worship a computer interfere with the space-castaways' efforts to tame a potential planet-destroying volcano. The premise is a sci-fi classic: a primitive culture guided by, and worshiping, an ancient technology that they don't understand, and the episode features some unique moments of awkward bro-bonding between Dr. Smith and Major West as together they face asphyxiation. Unfortunately, the story spirals into stupidity, in the second half, with the robot decked out in feathers 'dancing' with the cave people in front of some cartoonish 'totem poles' and performing 'magic tricks' in a 'robo a robo' with the malevolent e-brain. The cave people are typical sit-com fur-clad knuckle-draggers (they would have been at home in an episode of Sherwood Swartz's dire 'It's About Time (1966)) and one of Irwin Allen's faux dinosaurs (a tarted-up lizard from his unnecessary remake of 'The Lost World' (1960)) puts in an appearance. Whatever coherence the series had was collapsing from internal inconsistencies - since when can the robot simply materialise things from thin air? The episode was broadcast a couple of weeks before Star Trek' s similarly themed (but superior) 'The Apple'.