 From a planet completely dead for half a million years according to all previous data, the Enterprise hears the voice of Sargon, who is able to control the ship, telling them to visit to transporter coordinates he pre-set to a miles deep subterranean chamber; Kirk, Spock and McCoy do with the ships astro-geologist Ann Mulhall; the security guard they planned to take along was prevented from de-materializing. Sargon is one of only three survivors of the planets intelligent race -pure energy, matter without form- telling them they once started life on earth and many other places when still material, but annihilated their world once evolved far enough to believe themselves gods. Suddenly Sargon possesses Kirk s body, saying he requires Spock s and Ann Mulhall s to give the only other survivors of his race new life, promising the bodies will be returned after they build superior mechanical robots as their definitive bodies, then leaves Kirk s and allows them to beam up and freely make up their minds; only McCoy isn t tempted enough by curiosity and potential benefits, but Kirk convinces him to redraw his veto. However the human bodies need a metabolic reduction injection; the alien in Spock s body uses Vulcan mind control to make nurse Christine Chapel put a wrong formula in Sargon s, also dooming Kirk to death; his wife too asks Sargon if they must abandon real physical contact, before he dies- can Kirk be revived, as his mind is still in Sargon s mind-receptacle from the planet. The aliens have more surprises in store...