The episode starts out on the Enterprise bridge with lights flickering and the crew throwing themselves from side to side to simulate turbulence. Spock says some mumbo jumbo about the temporal fluctuations. Suddenly Sulu’s control panel explodes and he is hurled to the deck. McCoy gives him an injection of cordrazine and Sulu immediately responds and recovers. But another bump of turbulence causes McCoy to accidentally inject himself with a massive overdose of the drug which turns him into a raving paranoid fleeing imaginary assassins. In this state he overpowers a transporter operator and beams himself down to a planet in the vicinity of the Enterprise.
Kirk and Spock and a landing party beam down to the planet and discover a strange quadrilateral shaped stone aperture that talks and is the source of the time distortions. It says it is the Guardian of Forever and the aperture is a time portal through which it is possible to access the past. We see scenes that are supposed to represent ancient Egypt and Rome. But as the images begin to portray more modern times McCoy jumps out of the background where he is lurking and runs through the portal.
Just then Uhuru who very unusually is on this landing party tells Kirk that her conversation with the Enterprise has been interrupted. The Guardian informs them that McCoy’s entrance into the past has disrupted the time stream and the Enterprise and the whole Federation no longer exist. This puts a damper on the proceedings.
Spock says that using his “tricorder” readings he can allow himself and Kirk to jump into the past slightly in advance of McCoy’s entrance time and in that way, they can figure out how he disrupts history and hopefully prevent it.
They end up in 1930 New York City and meet Edith Keeler (played by a young and attractive Joan Collins) who runs a Street Mission, sort of a homeless shelter for the indigent during the Great Depression. She gives Kirk and Spock odd jobs to allow them to earn money. Spock uses their earnings to build a computer interface to extract information from his tricorder from the portal recordings he made earlier. When Kirk badgers him about his progress he replies that the available resources are primitive. Later when Edith sees his electronics project and asks him what he is doing he replies, “”I’m attempting to construct a mnemonic memory circuit, using stone knives and bearskins.” And that line may have been the highlight of the episode.
Right on schedule Kirk falls in love with Edith. And just then Spock discovers that the event that causes the alteration in time is McCoy preventing a car from running down and killing Edith Keeler. Surviving, she goes on to head a pacifist movement in the United States and thereby delays the United States entry into World War II long enough to allow the Nazis to invent the atom bomb and win the war. This puts another damper on the proceedings.
Shortly afterwards McCoy appears in the vicinity of the Street Mission and unbeknownst to Kirk and Spock Edith takes him in and shelters him at the mission. That night when Edith and Kirk are going to a Clark Gable movie, she mentions McCoy’s name. Kirk tells Edith to stay right where she is and runs back across the street toward the mission where, right on cue, McCoy and Spock are both standing on the street. The three shipmates joyfully meet but, just as any woman would, Edith disobeys Kirk and starts jaywalking across the wide street in the path of a speeding truck. Kirk looks up and is about to run to Edith when Spock warns him not to. Just then McCoy sees Edith’s plight and would have jumped to her aid except that Kirk subdues him with his arms. Edith is struck and killed and McCoy tells Kirk that he could have saved her and exclaims, “Do you know what you just did?” Spock speaks for the dazed Kirk saying in a subdued voice, “He knows, Doctor. He knows.”
The time travelers return to the Guardian of Forever who announces that the time stream has been restored to its original course. When the landing party contacts the Enterprise and asks Kirk for orders he sullenly replies, “Let’s get the hell out of here.”
This episode is known because the original script was written by a well-known science fiction author Harlan Ellison. And the episode won a Hugo Award which back then was still considered a distinction.
Despite the sobering ending, the show includes a number of humorous exchanges between Spock and Kirk and in general strikes me as extremely well written. There isn’t any Shatner mockery aspect worth mentioning so I ‘ll give this an 8 // 1.