"The Gamesters of Triskelion" is a second-season episode of the original science fiction television series Star Trek, produced after John Meredyth Lucas had taken over for Gene L. Coon as the program's operating producer at the latter's request, first broadcast January 5, 1968 and repeated May 3, 1968. Catalogued as episode #45, production #46, it was written by Margaret Armen and directed by Gene Nelson. Gerald Perry "Jerry" Finnerman was the director of photography for the installment, and his cinematography protege, Al Francis, was chief camera operator.
In this episode, Captain Kirk and his companions are abducted into slavery and trained to fight as gladiators for the gambling entertainment of three disembodied beings.
On stardate 3211.7, the Federation starship Enterprise is on a routine inspection of an unmanned station at Gamma II. Captain James T. Kirk, Communications Officer Lt. Uhura and navigator Ensign Pavel Chekov attempt to transport but disappear before the system is activated. After observing no signs of life from the station, Commander Spock orders the crew to instigate a sector-wide search for their missing crew members. They do not find the officers, but Spock discovers a faint ion trail leading to a nearby star system, and orders the ship to follow it despite the protests of Chief Medical Officer Dr. McCoy, and Chief Engineer Scott.
Meanwhile, Kirk, Uhura, and Chekov gain consciousness on a strange planet within a gladiator arena. They are attacked by four humanoids, and though the officers find their phasers inoperable, they are able to fend off the melee attacks. The fight is stopped by another humanoid that calls himself Galt, the Master Thrall of Triskelion. Galt informs the three they have performed well, and now will be trained to participate in games to entertain their masters, the Providers. Each is fitted with a shock collar that engages should they disobey the Thrall's orders. Uhura, Chekov, and Kirk are assigned individual drill Thralls, Lars, Tamoon, and Shahna, respectively; Uhura and Chevok find their assigned instructor antagonistic, while Kirk finds that Shahna -- once described as "the green-haired female warrior who gets the hots for Captain Kirk" -- shows some compassion for him. Kirk uses this to try to gain information about the Providers from Shahna during their drills by explaining the concept of freedom, but when she does open up, the Providers shock her through the collar. Kirk tries to appeal to Galt that he should have been the one punished for disobedience. When they are returned to their cells, Shahna expresses her appreciation for Kirk's attempt to take the punishment. When she moves to embrace him, Kirk knocks her out and uses the opportunity to free Uhura and Chevok and escape, but they are stopped by Galt, and shocked by their collars, with the disembodied voices of the Providers warning that escape is impossible.
The Enterprise arrives at the end of the ion trail above a habitable planet Triskelion. When Spock and McCoy attempt to beam down, the Providers ensnare the ship with a power beam and take over full control of the Enterprise. The Providers tell Kirk that his ship is now at stake in the arena games. Kirk decides to give them an wager they cannot refuse, and he suddenly finds himself in an underground chamber. The Providers turn out to be three disembodied brains sustained by machinery which hold the personas of the Providers. The Providers explain that they watch over the Thralls and for their entertainment, wager "quatloos" over battles between the Thralls. Kirk offers that if he and his two officers emerge victorious in battle with their drill Thralls, that the Providers will let him and his crew go while freeing all of the Thralls and instead using their power to teach the Thralls to become a free society, while if Kirk and his officers lose, the Providers can take his crew to use in further competitions. The Providers agree, but stipulate that Kirk must battle the three Thralls alone.
The match is quickly arranged, and as the Enterprise crew watches from above, Kirk is able to kill two Thralls and injure the third. The Providers replace the wounded Thrall with Shahna. Though Kirk is exhausted and does not want to kill Shahna, he manages to overpower her, and she offers him her surrender. The Providers show compassion and agree that Kirk fairly won the wager, and as promised, release his ship and the Thralls. Kirk gives Shahna a kiss and explains the Providers will help them become a free society before the crew is transported back to the ship.