Drugs, a bit of counterculture and the love life of Spock all combine to make one of the best episodes of the Star Trek series
Drugs, a bit of counterculture and the love life of Mr. Spock all combine to make one of the best episodes of the Star Trek series. The Enterprise arrives at Omicron Ceti III to investigate the status of a human colony. The planet is being bombarded with Berthold rays, a form of radiation that is deadly to human tissue. Therefore, the Enterprise landing party has no hope of finding anyone alive.
To their astonishment, they are greeted by the colonists, all of which appear to be hale and hearty. The level of astonishment rises even higher when McCoy reports that the colonists are in perfect health, even to the level that preexisting conditions have vanished. Spock is the first member of the crew to succumb to the spores, a plantlike creature that infects human bodies and grants immunity to the Berthold rays and repairs all body dysfunction. An additional effect is that it gives the infected person a mindset of complete tranquility. This causes Spock pain at first as it forces his human half to the surface, competing with his Vulcan half.
With the exception of Kirk, the rest of the landing party is quickly infected and they pass the spores up to the Enterprise. In a short time, with the exception of Kirk, the entire crew is infected and down on the surface. He is also infected, but the strong and negative emotion he experiences at the thought of leaving the ship destroys the spores. Kirk then tricks Spock into beaming back to the Enterprise and incites him to violence, which destroys the spores in Spock's body. Together, they beam waves down to the planet which irritates the humans, causing the spores to die in all of them.
One of the colonists is a female (Leila) that Spock had a prior relationship with. When they first meet he once again asserts his Vulcan nature and inability to show strong emotion. However, in some of the best scenes in the entire series, Spock hangs from a tree, talks back to Kirk and lies on the grass with his head in Leila's lap. Spock looks up into the sky and talks about what he sees from the romantic perspective rather than the scientific.
This is also one of the best acted episodes of the series, the plot device of the spores allow Shatner, Nimoy and Kelley to display a wider range of emotions than they could in other episodes. In combination with a solid plot, this makes it one of the best episodes of the series.

An Episode Full of Bliss
Which is better: to live a life of perfect happiness but no accomplishment? Or to live a life of achievement and progress yet never feeling content? This is one of the major questions of life. "This Side of Paradise" deals with it directly. An Earth colony has been zapped by a bunch of spores, which sustain life and induce blissful contentment in their hosts, but at a price. The spores take away all ambition, drive, and sense of duty.

You can imagine how, when the Enterprise visits the planet, the spores change Mr. Spock, who at first fights them. But he finally gives in. In his case, they let his human side, for the first time in his life, reign supreme, enabling him to return the love of a beautiful woman (Jill Ireland) who has adored him from afar. It is Kirk, not Spock, who finally overcomes the spores. This is a running theme in the series... Spock is superior to Kirk in many ways: intellectually, physically, spiritually. But it is Kirk's unconquerable will that makes him the leader of the Enterprise.

This episode is outstanding because of the subtle touches in DC Fontana's script and the marvelous way it is acted. Anyone who thinks Shatner is incapable of convincing acting should look at the scene in which Kirk says to the spore-influenced Spock, "Are you out of your mind?" while Spock hangs from a tree like a monkey.

But it is the last half that is more than worth the price of admission. First, the scene where Kirk drives the spores' influence out of Spock by calling him a "freak" and insulting his parents. (Y'see, strong negative emotions overcome the spores.) This is followed up later by perhaps the best-written scene in the entire Star Trek franchise: Spock explaining to Leila that he cannot go back. "If there are self-made purgatories, then we all have to live in them. Mine can be no worse than anyone else's."

The scene ends with the following exchange:

LEILA: (Weeping.) You never told me if you had another name, Mr. Spock.

SPOCK: (Pause. Touches her cheek.) You couldn't pronounce it.

Then there is the final line of the show. As they prepare to warp out, Kirk asks Spock what he has to say about their adventure. Spock responds that he has nothing to say, except: "For the first time in my life, I was happy."

"For the first time in my life, I was happy."
Happy is putting it mildly! See Spock swing from trees and engage in some serious lip-lock with Leila Kalomi! The care-free colonists of Omicron Ceti III have a secret -- they should have died of Berthold Rays, but they're all happy, healthy, and not at all concerned that all of their animals have died. Kirk gets to the heart of the matter (with Samsonite luggage in hand).
One of my favorite, favorite episodes of all time. This episode features one of the sweetest goodbye scenes ever. Guest stars include the lovely, and much missed Jill Ireland as Leila.

Another top notch episode from the end of season 1
Yet another excellent episode, this one concerns a planet where plant spores have caused an epidemic of joyful inebriation. Like many of the best early shows, the slow pacing here allows a sense of mystery to develop before the hook is revealed to us. This is one of the more convincing of the 'Enterprise in danger' episodes, but it is more than that. The plot device enables several crew members to flesh out their characters, most notably Leonard Nimoy. It is difficult not to feel angry at Kirk as he goads Spock with racial slurs, even as we understand why he says what he does. Certainly the conflict between the happiness provided by drugs and alcohol on the one hand vs. their 'unnatural' tendency to hinder personal development and achievement is as resonant today as it was in 1967.

Spock Does Hallucinogens -- and Jill Ireland
For the first time in his life, Spock has a good time. After Jill Ireland's character, Leila, tricks him into ingesting hallucinogenic spores, he smiles, laughs, plays in trees, marvels at clouds and sunsets, and becomes incredibly insubordinate to captain Kirk. He also falls in love with Leila.

Eventually, the entire crew, with the exception of the captain, succumb to the spell of the spores and abandon the Enterprise in lieu of an idyllic life on a peaceful planet.

This fun episode is a bit slow in parts, but Kirk's solution to the problem is one of those classic Trek moments. It must be viewed to truly appreciate. Over all, a very good episode.