"Errand of Mercy" is an episode of the original science fiction television series Star Trek. It was originally broadcast on 23 March 1967. It is episode #26, production #27, written by Gene L. Coon and directed by John Newland. This episode marks the first appearance of an alien race known as the Klingons.
At war with the Klingons, Captain Kirk and his First Officer, Mr. Spock, attempt to sway the incomprehensibly placid population of a planet to resist an invading military occupation.
Relations between the United Federation of Planets and the Klingon Empire have reached the breaking point, and recent negotiations have collapsed. The starshipEnterprise has been sent to the world of Organia, a non-aligned planet near the Klingon border, to prevent the Klingons from annexing it. As the Enterprise approaches Organia, Spock briefs Kirk, calling it a primitive society. Without warning, the Enterprise is attacked by a Klingon vessel, which is quickly destroyed when the Enterprise returns fire.
Upon arrival at the planet, Kirk leaves his helmsman, Lt. Sulu, in command of the ship with instructions to withdraw if a Klingon fleet should arrive. Kirk and Spock then beam down to the planet surface and find themselves in a primitive town, where the inhabitants do not respond to their means of arrival. Spock notes the "ruins in the distance," which is the Citadelle Laferrière in Haiti. Kirk tells the Organian council of what the Klingons will do if they capture the planet, but the Organians are unconcerned. Instead, the Organian leader says that the Enterprise and her crew are the only ones in danger. A Klingon fleet appears, firing on the Enterprise. Kirk orders Sulu to follow orders and to withdraw, which strands Kirk and Spock on the planet.
The Organians disguise Kirk as one of them and have Spock pose as a Vulcan merchant of trillium. The Klingons seize control of the planet without resistance and install the ranking Klingon officer, Kor, as the military governor. Kor, noticing that Kirk is the only Organian who doesn't smile all the time, takes a liking to him and demands that he act as the Organian liaison. Spock is taken for questioning to verify his background as a trader, but is able to resist the "mind sifter" device that the Klingons use.
The Organians do nothing to resist the occupation. Kirk and Spock start guerrilla operations of their own by blowing up a munitions dump outside of town. The Organians in the council strongly object to the action, while Kirk protests their lack of action. Meanwhile, Kor listens to Kirk's speech through a hidden camera, discovering that he is the saboteur.
When the Klingons threaten to torture them as suspected insurgents, the Organians reveal the true identities of Kirk and Spock and allow them to be arrested. Spock is imprisoned while Kirk is taken to Kor's private chambers, where Kor tells Kirk that he has twelve hours to answering questions about the Federation fleet. After that, if Kirk still refuses, he will undergo the mind scraping technique, leaving him a vegetable. Also, Spock will be dissected to determine how he was able to resist the mind probe.
With six hours remaining before the deadline, the Organians effortlessly free the pair and hide them in the council chamber. While Kirk and Spock try to comprehend the natives' contradictory actions, Kor retaliates by ordering the execution of two hundred Organians. Still, the Organians continue to protect Kirk and Spock, but remain otherwise unperturbed by the Klingons' actions, leaving the Federation officers and the Klingons alike baffled and frustrated.
As Federation and Klingon fleets converge on the system, threatening to turn it into a war zone, Kirk and Spock execute a daring raid on the Klingon headquarters in hopes of rousing the population into resistance. They capture Kor and preparing to make a last stand, while the fleets are ready to clash. The Organians then reveal their true nature: They are not primitive humanoids, but are highly advanced incorporeal beings. They instantly incapacitate both sides, not only around the planet but everywhere, forcing the two sides to agree to the Organian Peace Treaty. Both sides protest, but the Organians predict the two rivals will get along far better in the future. When Kirk says to Kor that it looks like they won't have their war after all, Kor responds, "A shame, Captain. It would have been glorious!"