The Gamesters of Triskelion

As Captain Kirk, Lieutenant Uhura, and Ensign Chekov are about to beam down on a routine survey mission, they are abducted by a powerful transporter beam. They arrive on the planet Triskelion in the trinary star system M-24 Alpha. Kirk and company learn that are to be used as gladiators, to fight in games staged for the amusement of "the Providers," the rulers of the planet. While Mr. Spock attempts to locate his captain, Kirk and his companions experience various ordeals, including excruciating pain inflicted by Galt, the master thrall. When the Enterprise arrives and orbits Triskelion, the Providers capture the starship. To save all aboard, Kirk proposes a wager with the Providers, who are actually aged and bored beings reduced to disembodied brains. Kirk is pitted against three thralls including Shanna, whom he has attempted to teach about love and loyalty. He wins the contest, the Provides free the thralls, and the Enterprise proceeds on its way.