"This Side of Paradise" is a first-season episode #24, production #25, of Star Trek: The Original Series. It was first broadcast on March 2, 1967 and was repeated on August 10, 1967. The episode was written by D.C. Fontana and Nathan Butler, and directed by Ralph Senensky.
On stardate 3417.3, the Enterprise arrives at Omicron Ceti III, where a Federation colony has been in place for several years. The planet however, is known to have been showered by Berthold rays, a deadly form of radiation which causes severe tissue damage within a few weeks of exposure. To make matters worse, there has been no communication with the colony for quite a while. The Enterprise's sad mission is to retrieve the colonist's remains and their equipment.
Captain Kirk, along with Dr. McCoy, Mr. Spock, Mr. Sulu, and a few other crewmen, beam down to the planet's surface and make the startling discovery that the colonists are still very much alive. The crew is greeted warmly by Elias Sandoval, a farmer & leader who assures them that there have been no problems other than a faulty communications system. They encounter another colonist, Leila Kalomi, who was a love interest of Mr. Spock's six years earlier back on Earth. At a loss to explain why these people are still alive, Dr. McCoy arranges to perform medical exams on a number of the colonists while other crew members search the vicinity for answers.
The puzzle deepens as McCoy finds the colonists in flawless health; in reviewing the colonists' medical records, he finds that, although the records indicate that Sandoval had had his appendix removed, his earlier examination showed Sandoval to have his appendix intact. The other members of the landing party discover that there is no animal life present — no livestock, no birds and no insects. Evading Kirk's questions about the fate of the farm animals they brought with them and the general absence of animal life on the planet, Sandoval explains simply, "We're vegetarians".
As Spock is searching the surrounding area for clues, the lovely Leila meets with him and agrees to show him how the colonists have survived. She takes him to a place where there are strange flowers that shoot a puff of spores at him.
Being half-Vulcan, Spock doesn't normally express his emotions, but moments after exposure to these spores, the formerly logical Spock is able to tell Leila, "I love you". Now free to find bliss with Leila, Spock laughs and with his head in Leila's lap he lolls under a tree with her as they contemplate the clouds. When Kirk attempts to contact him, it is not Spock but Leila who opens the communicator. Unwilling for a moment to stop embracing, nuzzling, and kissing Leila, Spock answers Kirk's questions with amused curtness and refuses to obey orders.
Spock shows the strange flowers to Kirk and other crewmen, but Captain Kirk escapes being hit by their spores as he is just out of range of their fire. When Kirk returns to his ship, it is full of the flowers and their spores. The entire crew, in an open but peaceful mutiny, begin to beam down to the planet. Before she leaves, Lieutenant Uhura sabotages the ship's communications system.
Soon, Kirk is the only person remaining aboard the ship. Since the ship is filled with the plants Kirk finds himself within range of one of them, and it shoots its spores at him. Kirk begins to feel at peace and makes plans to beam down to the colony, but as he is about to leave the Enterprise, he feels a wave of violent emotions which overwhelms and destroys the spores within him.
Kirk now realizes the spores cannot survive the presence of strong feelings. He asks Spock to come up to the ship ostensibly to help him with some things that they won't be able to retrieve once the last of them leaves. Kirk actually wants to talk some sense into Spock. The Captain states for his log that his plan to kill the spores by enraging Spock carries considerable risk: Spock is a half-Vulcan, a humanoid far stronger than a human, whose race were once ferocious warriors before their control of emotion ended the slaughter on their world.
Nonetheless, when Spock arrives, Kirk insults him with a stream of racist abuse and taunts him as a freak who dares to make love to Leila. Spock is angered and a brawl ensues but fortunately, his rationality returns to him before he seriously injures the Captain. They collaborate and create a device to send a subsonic frequency through the communicators that will irritate everyone in the colony. Soon, fights break out all over, which quickly ends the spores' influence.
After some time has passed and things return to normal, Spock asks Leila to come aboard the ship. She beams aboard only to find Spock no longer "With us" and desperately pleads with him to return to the planet so they can be together. Regretfully, he tells her he has responsibilities on the ship and can not. Leila begins to cry and says "May I say I love you, one last time?" Spock makes no objection and she embraces him. Then she asks if he has another name besides Spock. He takes her arms from around him and gently brushes a tear from her cheek. He smiles painfully and says, "You couldn't pronounce it".
As the Enterprise, with the colonists safely on board, prepares to exit the planetary system, Spock comments about his experiences saying: "For the first time in my life, I was happy".
This episode was re-mastered in 2006 and was first aired July 28, 2007 as part of the remastered 40th Anniversary original series. It was preceded one week earlier by the remastered version of "The Squire of Gothos" and followed after a several week break by the remastered episode "The Galileo Seven". Aside from remastered video and audio, and the all-CGI animation of the Enterprise that is standard among the revisions, specific changes to this episode also include: