Executive Producer: Gene Roddenberry
Producers: Gene L. Coon + John Meredyth Lucas
Associate Producer: Robert H. Justman
Script Consultant: D. C. Fontana

Story by: Jud Crucis
Writer: Gene Roddenberry
Dir.: Marc Daniels

Captain Kirk: William Shatner
Science Officer, First Officer, Cmdr. Spock: Leonard Nimoy
Dr. Leonard "Bones" Mc Coy: DeForest Kelly
Lt. Sulu: George Takei
Lieutenant Commander Montgomery Scott: James Doohan
Lieutenant Uhura: Nichelle Nichols
Nurse Christine Chapel: Majel Barrett

Tyree: Michael Whitney
Dr. M'Benga: Booker Marshall
Nona: Nancy Kovack
Mugatu: Janos Prohaska

Stardate: 4211.4

The Klingons are interested in a planet and plan to take it over. It is a peaceful planet that Kirk visited 13 years ago and befriended Tyree, the peace - loving leader of a tribe. In the hills dwells another tribe, not as peace – loving, who's members are called the Hill People. When Kirk, Spock and others beam down, they witness some warriors hiding behind rock in an ambush for others. Kirk throws a stone and causes one to shoot earlier than he intended to. Immediately the party heads for Spock and Kirk. On their way to Dr. McCoy, who takes samples, Spock is shot and severely hurt, his life is in danger. 

They beam back to the Enterprise and Spock's only chance to survive is to resort to Vulcan techniques to cure himself, because the help he can get on board is not sufficient, though Dr. M'Benga is an excellent doctor and very familiar with Vulcan medical conditions, anatomy and abilities. Dr. M'Benga knows which Vulcan way Spock uses in his attempt to heal himself and to survive. From him Sister Chapel learns that they cannot do much but to hope for the best and she tries to support and comfort Spock who seems unconscious. To her embarrassment Dr. M'Benga tells her that, though Spock seems to be unconscious, he notices all she does – including having held his hand. 

On the planet Kirk and McCoy wonder about the presence of advanced weapons used by the Hill People. There had to be influence from outside. His attempts to talk Tyree and McCoy into the need of fighting back fail. Then Kirk is bitten by a fury, one horned, big being, a mugatu. The bite is deadly and only Nona, Tyree's wife can heal him by her mystic ways. When Kirk encounters the Mugatu again while he is with Nona, she watches him taking his phaser to kill the animal. The moment Kirk is still down, she takes his phaser and wants to try it out during another attack of the Hill People. Seeing her going against the Hill People alone, Tyree follows her and watches his wife being killed because she's not used to operate the phaser quickly enough. Now he is heartbroken and changes his mind: He wants to fight them. The only thing the crew can do is to supply the same weapons to Tyrees people as the Hill People get from the Klingons to maintain a balance of power instead of reaching their true aim – a peaceful solution and living together of both sides. 

Spock is deep into the healing process as Dr. M'Benga tells the others. The doctor knows from his time of internship he spent on Vulcan that when the moment has come to bring Spock out of the trance he needs any wish of his to be fulfilled. "Any?" sister Chapel asks and Dr. M'Benga confirms. When Spock is half awake and needs to get out of trance, he asks sister Chapel to hit him. She first says she cannot do it and then tries, because Spock tells her it is the only way for him to get out of the trance. Sister Chapel begins to hit him. "Harder", Spock requests. The moment Mr. Scott enters, she tries and Scott holds her wondering whether she's gone insane. Dr. M'Benga comes in and takes over by beating Spock's face hard. He manages to awaken Spock and all are glad to see him cured.