The U.S.S. Enterprise finds the wreckage of the S.S. Beagle, with no survivors, orbiting near the Planet 892-IV. When Kirk, Spock, and McCoy beam to the planet's surface, they are captured and taken to the city which looks very much like Earth's ancient Rome. They find that Captain R.M. Merrick of the Beagle has betrayed his crew, beaming them down to fight in the Roman-like gladiatorial games. Merik has become First Citizen Merikus of the Empire and supposed close friend to the Proconsul, Claudius Marcus. Kirk realizes, however, that Merik is being used as a lure to get more starship crews to 892-IV for the entertainment of its inhabitants. When Kirk refuses to beam his crew down to die in the arena, Spock and McCoy are condemned to fight gladiators in the ring.

James Doohan (Lt. Cmdr. Montgomery Scott)
William Smithers (Capt. R. M. Merik/Merikus)
Logan Ramsey (Claudius Marcus)
Ian Wolfe (Septimus)
William Bramley (Policeman)
Rhodes Reason (Flavius)
Nichelle Nichols (Lt. Uhura)
Walter Koenig (Ensign Pavel Chekov)
Bart La Rue (Announcer)
Jack Perkins (Master of Games)
Max Kleven (Maximus)
Lois Jewell (Drusilla)