Series: The Original Series
Air Date: April 6, 1967
Written by: Harlan Ellison
Directed by: Joseph Pevney
Bones goes on a drugged rampage through time and Kirk and Spock go to find him and fix history.
While traveling over the planet Gateway (which is not named in the episode), the Enterprise experiences turbulence while passing through time distortions. The turbulence knocks out Sulu, so Bones comes in with some cordrazine and wakes him right up with just a couple drops. Unfortunately, the turbulence pushes Bones to accidentally inject the entire hypo into himself. The high dose of the "tricky" drug makes him go insane and run off the bridge, overtake the transporter technician and beam down to Gateway. So Kirk, Spock and the whole team is forced to follow.
While they're looking around on the surface, they find The Guardian of Forever. It's a big arch-like thing that talks and acts as a portal through time. Also, it's very cryptic. Apparently it's been around since before our sun and has been waiting all this time for a question. So Kirk poses one to it: "Are you a creature or a machine?" And it answers: "I am both. And neither." So Spock gets tired of the riddles and says "screw this!" while proceeding to study it with a tricorder.
|AND THIS IS THE DARK ERA IN WHICH YOUR SPECIES|
WAS OBSESSED WITH JERSEY SHORE.
Unfortunately, for as advanced a thing as the Guardian is, it can't get a good lock on where Bones ended up, so Spock has to make his best guess. And they end up a few weeks in the past from where Bones went. It's Depression-era America, so the first order of business is to act like a bum to fit in. How do they do that? By stealing clothes and finding shelter at a soup kitchen.
|I swear, they were on sale.|
Meanwhile, Kirk is falling in love with Edith Keeler. Which is unfortunate, because Spock finds out that she is the fork in the timeline. When Bones arrives, he's going to save her from a car accident and she'll go on to start a massive pacifistic movement that makes America late in entering World War II, thus allowing Germany to finish the H-bomb and take over the world. Kirk is mortified that in order to save the world, Edith Keeler must die.
|"Did you know that in French the word for 'orgasm'|
translates literally as 'the little death'?"
History corrected, the Guardian brings them back to their own time where Scotty and Uhura are waiting. As is the Enterprise and all of Starfleet. The Guardian offers his talents to help Starfleet explore history, but Kirk doesn't care. He just watched the love of his life get hit by a truck. Leave him be.
It's another story of personal sacrifice. This time of a completely different nature. Really it's Kirk's own fault. He needs to stop falling in love with women from the past. They're only trouble. The story told here ends up being the format for several time travel stories in several franchises to come. It's good to know that this episode of Star Trek had such an effect on sci-fi writing.