The Enterprise prepares for the evacuation of doomed planet Sarpeidon, but Captain Kirk (William Shatner), Mr. Spock (Leonard Nimoy), and Dr. McCoy (DeForest Kelley) find that all inhabitants have left via a time-travel device that has sent them to different periods of their own choosing. Kirk, Spock, and McCoy accidentally pass through the device, with the captain landing in the middle of an 18th-century-style witch-hunt while Spock and McCoy travel back 6,000 years to the Ice Age.
The script, by UCLA librarian and spec writer Jean Lisette Aroeste (who also wrote "Is There in Truth No Beauty?" for the original series), gives the episode a special charge with its dual story lines set in the past. The dramatic weight of the story, however, is clearly with Spock, who regresses into the savage emotions of his prehistoric ancestors--eating meat, choosing another transportee (Mariette Hartley) as a mate, and nearly killing McCoy when the good doctor insults him. This is a favorite among some Trekkers, made all the more enjoyable by the anxious, White Rabbit-like performance of Ian Wolfe as a Sarpeidon librarian in charge of the time-travel facility. --Tom Keogh
From the Back Cover
When Spock and McCoy try to rescue Kirk from a time machine accident, they emerge in an ice age. Spock, now a throwback to earlier Vulcan times, falls in love and refuses to return to Kirk or the starship.
Emmy Award-winning actress Mariette Hartley (Zarabeth) later appeared as James Garner's wife in a series of tremendously popular Kodak commercials.
The viewer on Mr. Atoz' desk is Sargon's stand from "Return to Tomorrow" upside down!