The standard-bearer for the entire Star Trek canon, this episode begins with a medical accident that leaves Dr. McCoy (DeForest Kelley) a paranoid madman. Leaping through a time portal to Earth's Great Depression of the 1930s, McCoy causes disastrous changes to history that include the disappearance of the Enterprise. Captain Kirk (William Shatner) and Mr. Spock (Leonard Nimoy) must follow him and undo whatever disruptive action he took centuries before. There, Kirk meets a kindly social worker, Edith Keeler (Joan Collins), with whom he falls in love before realizing that her fate is the key to a restored future.

Not the book but a classic Episode 28

In the program McCoy accidentally injects himself with substance that makes him paranoid and is compelled to leave the ship for the planet they are near. Through a series of events he goes through a portal to old earth (depression era). Some how he changes history and the Enterprise disappears. So the mission is to retrieve McCoy before he changes time. This naturally includes a love interest (Joan Collins.)

Read the book on Harlan Ellison's Manuscript first (ISBN: 1565049640). This is not a serialization of the program; it is the original written script. You will be surprised at the transformation from a Harlan Ellison novel to a Star Trek episode (28).
To fit the mold of the series McCoy replaced a drug dealer. The first thing Harlan asked was that if clothes were stolen that they did not look like they were miraculously a perfect fit. And Spock stops Kirk from saving Edith. Kirk would have given up the future for love.

Now watch this episode, and yes the changes were necessary and this is one of the best.

The Best of the Best

This episode is the best of the best. Other episodes as well as other TV shows have come and gone. But "City" will last and last. But what I'm really writing this for is to tell you to get the DVD version. DO NOT get the VHS version. Some of the incidental music was changed. Instead of the classic song "Goodnight Sweetheart", they substituted some dumb song. Completely ruined the show. I threw the tape I bought in the garbage. Literally. But, I now have a DVD copy which is completely original. Get the DVD !!!

I agree. Absolutely the best of the original Star Trek

episodes. Maybe even the best of the "time travel" genre. I love the original Star Trek, over & oover & etc. Production values low but the stories are so superb & original it doesn't matter. But this episode is the best of those. Joan Collins was once a babe & this is her best work. The Star Trek series that have followed have used & reused the the plots from the original merely requiring some rewrite. But they haven't attempted this one. How could they? The world-wide depression, the rise of facism, WWII pending, all are actual events from history. They must be allowed to proceed or the world that Kirk & Spock know will never exist. Pretty heady stuff for a t.v show.