Alien blobs refigure themselves as the Jupiter 2's crew and steal the saucer in order to infiltrate, and ultimately conquer, Earth. The episode is on par with most of those presented in season 3: a flimsy, patched together story, recycled footage, and an annoying reliance on characters being able to appear and disappear at will (presumably to avoid the cost and time involved in filming them moving). Little attempt is made at internal consistency (the landing site of the Jupitar 2 varies with perspective, the 'space-pod' seems to be in two places at once, chairs designed for human butts in the butt-less blobs's base, etc.) and the storyline seems to contradict the show's basic premise: if the aliens, who have not encountered humans before, can fly the Jupitar 2 to Earth, then surely the Robinsons could as well (the 'lost' ship's navigation computer must know the location of the planet and the ship must have sufficient 'deutronium' fuel to make the trip). Unfortunately, as usual too much running time is spent on 'Smith and robot' shtick to allow for the kind of exposition needed for the stories to make even rudimentary sense.