All Our Yesterdays ( episode ) Kirk , Spock , and McCoy are trapped in a planet ' s distant pasts , where Spock finds love with an exiled woman . Summary . Teaser . Captain Kirk , Spock and Doctor McCoy transport to the surface of the planet Sarpeidon , to warn the inhabitants that their sun ( the star Beta Niobe ) is about to become a supernova which will destroy the planet . All three members of the landing party are surprised to find there are no inhabitants of Sarpeidon remaining . In a Sarpeidon library , the team encounter a librarian named Mr . Atoz and several of his replicas . Act One . Mr . Atoz tells the three men from the that the planet ' s population had been warned about the impending supernova and has escaped by traveling into the planet ' s past using a time portal called the atavachron . Kirk and McCoy are intrigued by the library and start exploring the small discs which archive the planet ' s past . Kirk is viewing a disc of an era that resembles 17th century England on Earth , while McCoy is viewing one detailing the Sarpeidon Ice Age . Kirk offers to evacuate Atoz , but Atoz tells them to hurry up and pick a destination and that he himself plans to join his wife and family when the supernova comes . Suddenly , a scream is heard coming from the outside of the library . Kirk runs toward it through some type of portal and is transported to the era of the disc that he had been viewing . Spock and McCoy immediately follow after him , and appear in a frozen wasteland . As it turns out , Spock and McCoy have traveled five thousand years into the past when the planet was in an ice age . Meanwhile , Kirk has " rescued " a woman from being stabbed with a sword by challenging her attacker to a sword fight . Only after chasing the man away does Kirk discover that the woman was a thief attempting to rob the man and he cannot find the entrance back to the library . Act Two . Kirk goes to the wall from which he had emerged and is able to talk to McCoy and Spock , but cannot get to them . When Kirk is arrested by the authorities for aiding a thief , McCoy and Spock ask him what is going on , and the authorities can also hear the voices . The woman then betrays Kirk and denounces him as a witch , claiming that he and the " spirit s " made her steal against her will . Kirk is forcefully taken away . Meanwhile , Spock and McCoy try to find shelter while stuck in Sarpedion ' s ice age . McCoy falls down , his hands and face are frostbitten and he cannot feel his feet . McCoy asks Spock to abandon him and find Kirk himself but Spock refuses . Just then , a figure clothed in a jacket and hood emerges from the snow and leads them to a heated cave . Spock has McCoy put onto a bed and wraps him up in a blanket . The figure removes its hood and jacket , revealing it to be a beautiful woman named Zarabeth . While McCoy sleeps , she informs Spock that she has been exile d to the ice age because one of her kinsman tried to assassinate Zor Kahn , the tyrannical leader of her time . While in prison , Kirk is questioned by the Prosecutor . When Kirk mentions the library , the Prosecutor becomes extremely uncomfortable . At first , he tries to maintain that Kirk might indeed be innocent . But when the guard insists that he heard voices talking to Kirk , he is forced to back off . When Kirk then starts repeating the word " library " to the Prosecutor , the Prosecutor gets flustered and rushes out , saying he wants nothing to do with Kirk . Act Three . Meanwhile , in the ice age , Spock tells Zarabeth that he must find his captain and get back to his own time . He proposes that she join him and the doctor and find the time portal . He will have the both of them immediately beamed up to the " Enterprise " upon making it to the future . However , Zarabeth tells Spock that the atavachron alters a person ' s structure and that he therefore cannot return to the future , as he will die . At the same time , Kirk escapes from his cell when he grabs the guard who is trying to pour soup into his bowl , steals his cell keys , and knocks him out . Kirk hides the guard ' s body to the side of his cell just as the Prosecutor arrives to take Kirk to the inquisition . However , Kirk overpowers him as well . He questions him and comes to realize that he too had also been sent from the future . Kirk threatens to denounce him as a witch as well if he does not help get him back to the library . The Prosecutor then informs Kirk that the atavachron alters cell structure and brain patterns to prepare people for their journey into the past . The Prosecutor had been " prepared " before crossing and cannot return without immediately dying , but when Kirk announces that he hadn ' t been similarly prepared , the Prosecutor tells him that they must get him back to the future immediately . If not , Kirk can only survive for a few hours in the past . The Prosecutor then leads Kirk back to the brick wall from which he had emerged . The Prosecutor says he cannot go any further and backs away while Kirk steps back into the library and returns to his own time . He meets one of the Atoz replicas , who insists again that Kirk be prepared , and Kirk is forced to lock him in a closet . Another replica appears and Kirk knocks him out . The real Atoz then appears and stuns Kirk with a cylindrical weapon . Act Four . In the ice age , Spock ' s personality is beginning to change . He falls in love with Zarabeth and believes her when she tells him he cannot go back . McCoy notices the changes in Spock ( especially when Spock responds to a typical insult from the doctor by grabbing him by the scruff of the neck and announcing " " I don ' t like that " " ) and guesses that Zarabeth is not being completely truthful in order to keep Spock with her . Spock also begins to notice that he is not himself after he eats meat and enjoys it . However , even with this knowledge in hand , Spock continues and proceeds to tell Zarabeth that she is beautiful and embraces her . While kissing her , he then begins to further emote and smiles . Meanwhile , Kirk has managed to recover enough from the stun blast to avoid having Atoz wheel him back into the atavachron . He overpowers Atoz and forces him to help him locate Spock and McCoy by trying out various discs in the viewer . McCoy has begun to realize that it is only Zarabeth who cannot return and confronts Spock with this fact . When McCoy also confronts Zarabeth and tries to force her to admit the truth to Spock , Spock grabs McCoy and flings him against a wall with his hand around his neck . McCoy then asks Spock if he ' s trying to kill him and if that ' s what Spock really wants . Spock angrily asserts that this is impossible for him to be acting like this because he ' s a Vulcan . McCoy reminds Spock that the he knows won ' t exist for another five thousand years and then asks Spock what ' s happening there at this very moment . Spock remembers his ancestors at that point were warlike barbarians and McCoy tells Spock he ' s reverting to the ways of his ancestors , five thousand years before he was born . Spock says he has lost himself and does not know who he is anymore . He then asks Zarabeth if it ' s possible for them to go back . She says she doesn ' t know definitively but McCoy says he ' s going to try to find the portal because that ' s where his home and life is . Spock agrees finally to go with him and Zarabeth accompanies them as well . When they find the area where they had came into the past , and where they once again hear Kirk call out to them through the atavachron , Spock can ' t bring himself to leave Zarabeth alone in the past . But she once again tells Spock that if she were to cross through the portal she would immediately die . Kirk calls to McCoy and Spock and tells them they ' ve got to come back , that it ' s almost time for the supernova . Spock tries to send McCoy on ahead but McCoy can ' t go through . Mr . Atoz realizes that they can ' t come back separately because they had gone through together initially . Finally , Zarabeth turns and leaves them behind and Spock reluctantly goes with McCoy back through the portal . Zarabeth turns around and takes one last look at Spock , with a tear running down her cheek . With everyone back , Atoz puts in a disc , pushes Kirk , Spock , and McCoy out of his way , and rushes to join his family before it is too late . Kirk tells McCoy that Atoz had his escape well planned , and that Kirk is glad he made it to where he was going . He then begins to call the " Enterprise " to have Scott beam them up . Spock tells McCoy that there ' s no need to watch him anymore , that he has fully returned to the present . McCoy tells Spock that it did happen though , and Spock agrees , but that it was five thousand years ago and Zarabeth is dead now , dead and buried , long , long ago . On Kirk ' s communicator Scott tells Kirk " " It ' s now or never . " " Kirk orders them to be beamed up and to have the " Enterprise " taken to maximum warp as soon as they ' re aboard . The landing party is beamed up and the " Enterprise " warps out of orbit just as Beta Niobe begins its supernova explosion and Sarpeidon disappears . Memorable quotes . " " A library serves no purpose unless someone is using it . " " " " You ' re a very agile man , Mister Atoz ! Just how many of you are there ? " " " " We ' re in a wilderness of arctic characteristics . " " " " He means it ' s cold ! " " " " Away ! Away , spirit ! And let honest men approach . " " " " We go together . " " " " You stubborn , thickheaded Vulcan ! " " " " I ' m called Spock . " " " " Even your name is strange . " " " " Do you know what it ' s like to be alone , " really " alone ? " " " " Yes . I know what it is like . " " " " What is this island ? " " " " It ' s called Earth . " " " " I know no island Earth . No matter . Continue . " " " " I heard the spirit talk to him . He answered . . . and did call it " Bones " ! " " " " Witch ! ! Witch ! ! They ' ll burn ya ! " " " " Don ' t let him doctor you . I ' m the doctor around here . " " " " And known as the worst patient in the entire crew of the " Enterprise " . " " " " Now you listen to me , you pointy - eared Vulcan ! " " " " I don ' t like that ! I don ' t think I ever did , and now I ' m sure ! " " " " What ' s happening to you , Spock ? " " " " Nothing that shouldn ' t have happened long ago . " " " " You are beautiful . More beautiful than any dream of beauty I ' ve ever known . " " " " Spock , you ' re reverting into your ancestors five thousand years before you were born ! " " " " I know I ' m going to try , Spock , because my life is back there . And I want that life . " " " " And she is dead now . Dead and buried . Long ago . " " Background information . Remastered information . The remastered version of " All Our Yesterdays " aired in many North American markets during the weekend of . While the episode required very few new effects , the planet Sarpeidon was given a CGI - makeover as was its sun , Beta Niobe . When that star goes nova at the end of the episode , dramatic new effects were inserted into the episode , based upon photographs taken by the Hubble Space Telescope . Initially , when Beta Niobe explodes , Sarpeidon glows before disappearing . And in the remastered version , Sarpeidon crumbles into dust from the supernova blast . Links and references . References . angler ; animal flesh ; atavachron ; Atoz ' s family ; Beta Niobe ; " Bones " ; boulder ; class M ; cook ; Earth ; food and clothing animals ; frostbite ; greenhouse ; horse ; hot spring ; Inquisitional Tribunal ; ; jailer ; kinsman ; librarian ; library ; license ; logic ; lord ; mass suicide ; meat ; medicine ; mort ; ; patient ; physiology ; pre - warp civilization ; replica ; sapient lifeform ; Sarpeidon ; Sarpeidon Ice Age ; spirit ; supernova ; tape viewer ; time portal ; tyrant ; verism tape ; Vulcan s ; ; witch ; witchcraft ; Zarabeth ' s kinsmen ; Zor Kahn