 The two books followed the original series episode "", and "Time For Yesterday" is subtitled The Yesterday Saga, Book 2.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 "Enterprise" is placed under the temporary command of Admiral Kirk and detailed to transport a powerful telepath to the Guardian.