Kirk, Uhura and Chekov are trapped on a planet where abducted aliens are enslaved and trained to perform as gladiators for the amusement of bored, faceless aliens.
Peaceful, primitive peoples get caught up in the struggle between superpowers, with Kirk unhappily trying to restore the balance of power disrupted by the Klingons.
The Enterprise is guided to a distant, long-dead world where survivors of an extremely ancient race - existing only as disembodied energy - desiring the bodies of Kirk, Spock and astro-biologist Ann Mulhall so that they may live again.
Looking for a missing Federation cultural observer, Kirk and Spock find themselves on a planet whose culture has been completely patterned after Nazi Germany.
Galactic alien scouts capture the Enterprise for a return voyage and a prelude to invasion. Kirk's one advantage - they're not used to their adopted human form.
Responding to a distress signal, Kirk finds Captain Tracey of the U.S.S. Exeter violating the prime directive and interfering with a war between the Yangs and the Kohms to find the secret of their longevity.
Kirk and a sub-skeleton crew are ordered to test out an advanced artificially intelligent control system - the M-5 Multitronic system, which could potentially render them all redundant.
Trapped on a planet whose inhabitants are descended from Northwestern Native Americans, Kirk loses his memory and is proclaimed a God while the crippled Enterprise races back to the planet before it is destroyed by an asteroid.
Lovely telepath Miranda is aide to Ambassador Kollos, in a box to stop insanity when humans see Medusans. She rejects Larry, a designer of Enterprise, and senses murderous intent nearby.
As punishment for ignoring their warning and trespassing on their planet, the Melkot condemn Capt. Kirk and his landing party to the losing side of a surreal recreation of the 1881 historic gunfight at the OK Corral.
Both humans and Klingons have been lured to a planet by a formless entity that feeds on hatred and has set about to fashion them into a permanent food supply for itself.
After Dr. McCoy helps the leader of a planet populated by people with powerful psionic abilities, they decide to force him to stay by torturing his comrades until he submits.
While transporting an arrogant, demanding princess for a political marriage, Captain Kirk must cope both with her biochemical ability to force him to love her, as well as sabotage on his ship.