Plot

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.

When the Enterprise trespasses into uncharted territory, Kirk, Spock, McCoy, Scott and Chekov are transported to a location that has all the trappings of the American Old West. It's October 26, 1881, and Kirk soon realizes they are in Tombstone, Arizona, on the day of the famed gunfight at the OK Corral between the Clanton gang and the Earps - with Kirk and company representing the ill-fated Clantons. If history is to be repeated, they will fairly all be killed so must use whatever resources availed to them to defeat the threat and survive. The solution, however - and the only way of escape - lies within them.—garykmcd

The Enterprise encounters a sophisticated buoy, placed by the highly advanced Melkot, who make clear by telepathy to have decided their territory is encroached upon, with the Federation 'intruders' considered a 'disease' that must be destroyed. The landing party, comprising Kirk, known to be in command, Spock, McCoy, Scott and Chekov, is sentenced without trial. They find themselves transported into a recreation of Tombstone, Arizona in October 1881, the site of the fight at the OK Corral, where they're apparently to die according to the pattern of ancestral violence the Melkotian culled from Kirk's mind, casted Kirk and his party as the Clanton clan which opposed the Earp family and got exterminated. Can history be changed in this reenactment? The crew is still in its own uniforms, so Kirk tries to avoid the fatal fight by talking sense and denying to be Clantons, but the five o'clock showdown remains and a forcefield prevents them from leaving town. They decide to prepare tranquilizers to fight without killing, but Chekov, alas, friendly to responsive local girl Sylvia, gets shot dead by Wyatt Earp, which Spock finds out of keeping with historical records and, therefore, clear proof their outcome is not preset. Kirk mistrusts everything now. At his insistence, the tranquilizer is tested on Scott - to no effect, which Spock knows is scientifically impossible. As the forcefield corrals them to the scene of their impending deaths. Spock concludes that physical laws have been suspended, which imposes a crucial conclusion.—KGF Vissers

The Enterprise encounters a sophisticated buoy, placed by the highly advanced Melkot, who make clear by telepathy to have decided their territory is encroached upon, with the Federation 'intruders' considered a 'disease' that must be destroyed. They had given a warning to the Enterprise to withdraw, but Kirk persisted since he was under orders to make "contact" with the Melkotians.

The landing party, comprising Kirk, known to be in command, Spock, McCoy, Scott and Chekov, is sentenced without trial. They cant contact the Enterprise as none of their instruments work. They find themselves transported into a recreation of Tombstone, Arizona in October 1881, the site of the fight at the OK Corral, where they're apparently to die according to the pattern of ancestral violence (Kirk's own familial ancestors died at TOmbstone when they settled the American mid-west) the Melkotian culled from Kirk's mind, casts Kirk and his party as the Clanton clan which opposed the Earp family and got exterminated. In 1881, 2 clans fought for the control of the Tombstone town. The Clantons lost that fight. Can history be changed in this reenactment? The crew is still in its own uniforms, so Kirk tries to avoid the fatal fight by talking sense and denying to be Clantons, but the five o'clock showdown remains (in which the Earps defeat the Clantons and shoot them all dead) and a force-field prevents them from leaving town.

They decide to prepare tranquilizers to fight without killing, but Chekov (as the alias Billy Claiborne), alas, friendly to responsive local girl Sylvia (Bonnie Beecher), gets shot dead by Wyatt Earp (Ron Soble) (who is also the Federal Marshall, hunting for the Clantons) (Sylvia was liked by Morgan, Wyatt's brother and Wyatt shoots Chekov when Sylvia proposes marriage to him), which Spock finds out of keeping with historical records (As Chekov's character actually survived the shoot out at OK Corral) and, therefore, clear proof their outcome is not preset. In addition to Wyatt, the Earps have Morgan (Rex Holman) (a sharpshooter) and Virgil (Charles Maxwell). Kirk figures that the Enterprise must be scanning the planet, trying to locate them, so they try to find the position there they beamed down to the planet surface. Kirk also instructs McCoy to create a tranquilizer using snake venom and tranquilizers. McCoy gets the ingredients at Doc Holliday's (Sam Gilman) clinic. At his insistence, the tranquilizer is tested on Scott - to no effect, which Spock knows is scientifically impossible.

Kirk tries to get the town sheriff John Behan (Bill Zuckert) to call off the fight, but Behan says that the town is looking to Clantons to get rid of the Earps. Kirk wants Sherrif to organize the town people against Earps, and Sherrif says that the Clantons have gone yellow against the Earps. The Sherrif says Clantons can kill the Earps any way they want and there would be no questions asked. the force-field corrals them to the scene of their impending deaths. Spock concludes that physical laws have been suspended, which imposes a crucial conclusion. The scenario is not bound by physical laws and is thus unreal. Chekov died since his mind told him he is dead, and not the lead shot. If they decide to not accept death, they will not die. Spock mind melds with everyone to ensure they believe that the bullets and the guns facing them are not real. The Earps arrive and start shooting, but cant kill Kirk and his men. Kirk beats the Earps and spares their lives. The entire landing party (with an alive Chekov) is transported back to the Enterprise.

The Melkotians are convinced that Kirk and his crew are peaceful and welcome them to their planet with welcome party.