Spock diverts the Enterprise to Starbase 11, where Kirk discovers that Spock's former commander, Christopher Pike, has been seriously injured and disabled by exposure to delta rays, experienced while saving a class of cadets. Pike is now confined to an elaborate life support apparatus. Spock abducts Pike and locks the Enterprise on a course for Talos IV, the only planet subject to General Order 7: visiting the world is a capital crime. Spock refuses to explain his actions, but demands a court martial, during which he presents evidence of an earlier visit. War, thousands of centuries ago, devastated the planet, and it was only now becoming able to support life again. Its inhabitants, forced underground, had developed enormous mental powers, including the ability to place illusions within the minds of others. Their plan was to breed a race of slaves to help them reclaim their world, as they were fragile and their civilization degenerate: illusions had proved a kind of narcotic. To this end, they kidnapped Captain Pike years ago...

Dr. Leighton calls Enterprise to his home on Planet Q with the promise of a new food source that could end hunger. But this is a ruse: Leighton is one of the few remaining survivors of Kodos the Executioner, who used a planetary famine to apply his own ideas of eugenics on Tarsus IV years earlier. A burned body convinced authorities that Kodos had died then, but Leighton is certain that actor Anton Karidian is Kodos. Kirk is less than amused at the deception - and then someone murders Leighton. It's not enough to accuse, but it is enough for suspicion, so Kirk arranges to strand the acting troupe, and then offers them a ride on Enterprise where he hopes to ascertain whether Leighton's accusation is true.