"All Our Yesterdays" is the twenty-third and penultimate episode of the third season of the American science fiction television series Star Trek. Written by Jean Lisette Aroeste and directed by Marvin Chomsky, it was first broadcast March 14, 1969. In the episode, Captain Kirk, Spock and Dr. McCoy are trapped in two timeframes of another planet's past. It guest-stars Mariette Hartley as Zarabeth and Ian Wolfe as Mr. Atoz. Plot The Federation starship Enterprise arrives at Sarpeidon, whose star will soon go nova. Kirk, Dr. McCoy and Spock beam down, encountering one resident, a librarian named Mr. Atoz. Aware of the imminent destruction, Atoz tells the landing party that he will soon rejoin his family. Atoz shows them the Atavachron, a time portal. Hearing a woman scream. Kirk runs through the portal followed by McCoy and Spock. Kirk finds himself in a period similar to 17th century England while McCoy and Spock travel back 5,000 years to Sarpeidon's ice age. They cannot locate the portal, but can speak to each other. Spock surmises that the Sarpeidons escaped to their past. The woman who screamed is a thief. The policemen who arrest her hear Kirk speaking to his friends and suspect he is a witch. In jail, Kirk mentions the Atavachron to the prosecutor. The prosecutor is also from the future, but explains that returning would be fatal; the time travel preparation changes the traveler's biology. Because Kirk was not prepared, he cannot survive for more than a few hours. The prosecutor brings Kirk to the portal. McCoy and Spock are saved by Zarabeth, a woman who takes them to a cave. Spock displays uncharacteristic emotionalism, falling in love with Zarabeth and growing angered by McCoy's slurs. Zarabeth is also from Sarpeidon's future, but was banished to this era, in which she is the only humanoid. She claims the Atavachron is a one-way trip. Spock accepts this, but McCoy accuses Zarabeth of lying because she is desperate not to be abandoned. McCoy realizes that being brought into the past is causing Spock to revert to the barbarism of the ancient Vulcans. Realizing the emotionalism of his behavior, Spock asks Zarabeth again about the portal. She admits she does not know how a return trip will affect them. Despite Kirk's explaining they are not from Sarpeidon, Atoz tries forcing him back into the portal. Kirk overpowers Atoz and forces him to find