Time for Yesterday " Living in the past , dead to the present , only Spock ' s son can save the future ! " Time for Yesterday is a Pocket TOS novel – # 39 in the numbered series , and the second book in the retroactively designated " Yesterday Saga " – written by A . C . Crispin . Published by Pocket Books , it was first released in . Summary . The Guardian of Forever has malfunctioned and is emitting waves of accelerated time that are causing premature star deaths throughout the galaxy . After Spock recalls that his son Zar was once able to communicate telepathically with the Guardian , the is placed under the temporary command of Admiral Kirk and detailed to transport a powerful telepath to the Guardian . The telepath manages to partially restore the Guardian ' s timetravel functions but collapses in a comatose state . Using the time portal , Kirk , Spock , and Dr . McCoy travel into the past of the planet Sarpeidon to find Zar , hoping that his powerful telepathy combined with Vulcan shield training will allow him to successfully restore the Guardian to its normal state while protecting himself from adverse effects . They find Zar in charge of a small , technologically advanced settlement that is about to engage in a battle with an alliance of less advanced but more numerous enemy clans . His death in the coming battle has been foretold by the priestess Wynn , the daughter of one of the enemy clan chiefs , who declares that the alliance will be denied victory only if " he who is halt walks healed " and " he who is death - struck in battle rises whole . " " He who is halt " clearly refers to Zar , who walks with a painful limp because of a leg injury he suffered many years before . In order to increase his city ' s odds of survival , Zar marries Wynn , forcing her father to change sides . The Enterprise crew manage to convince him to come back with them and deal with the Guardian , although he insists that he will return afterward to fight in the battle despite the prophecy . Zar successfully achieves a mind meld with the Guardian and returns its consciousness to its physical structure , along with a burst of power that turns out to be several beings of pure energy exiting from the portal . The Guardian explains that it abandoned its duties to search for its Creators , who long ago evolved into pure energy and entered another dimension . Its fundamental programming required it to answer their summons and bring them home , resulting in its apparent malfunction . They wish to find their home planet , but they have forgotten where it is . In order to converse with Zar and the " Enterprise " crew , the Creators assume the form of people drawn from their memories , such as Zarabeth , Sam Kirk , McCoy ' s ex - wife Jocelyn , and Kirk ' s mother Winona . While some of the beings act in a benevolent manner , a few are capricious and cruel . Eventually , Kirk and the others manage to convince them that their search would endanger intelligent life throughout the galaxy , and they re - enter another dimension via the Guardian . The Guardian , with the assistance of Zar and Spock , is able to force the less benevolent Creators to comply . McCoy convinces Zar to undergo treatment and physical therapy aboard the " Enterprise " , healing his leg and giving him a greater chance of survival in the coming battle . Zar achieves peak physical condition and is able to walk normally again , fulfiling the first half of Wynn ' s prophecy . When he returns to Sarpeidon ' s past , Spock secretly follows him , intending to help save him in the battle . He brings with him two of the ancient Vulcan weapons from his collection , the lirpa and the ahn - woon . Spock is unable to prevent the death - blow from landing , although he manages to deflect it slighty , and Zar is unconscious but still alive . In order to fulfill the second half of the prophecy , Spock puts on Zar ' s armor and shows himself to the army , leading them to believe their leader has risen from the dead . Zar ' s army wins the battle . After ensuring that Zar will survive the blow and leaving him to Wynn ' s care , Spock returns to the present . References . Guardian of Forever ;