Two years after the U.S.S. Enterprise's visit to the dying planet Sarpedion, a young crew member finds evidence that, when transported to the past during his time there, Spock fathered a son. Determined to rescue the boy and his mother, Spock, Kirk, and McCoy use the Guardian of Forever to journey to the planet's prehistory, where they meet Zar, Spock's son, and bring him back to their time. Though Zar acclimates quickly to his new surroundings, bonding with his father proves difficult until an incursion by the Romulans forces the two to work together — and Zar to confront his future.
A.C. Crispin's novel was one of the first of the Star Trek Pocket Books series that I read, and one of the ones I remembered most fondly. I was a little worried that revisiting it would cheapen my recollection; instead it only deepened my appreciation of what the author achieved with it. Crispin manages to achieve an ideal balance between the original series (integrating details and characters from five episodes) and her own creations for the book. Foremost among the latter, of course, is Spock's son Zar; while not an original idea (with the introduction of Kirk's son in the movie Wrath of Khan predating this book by a year), he is introduced in a way that is extremely faithful to the series. Yet the strongest element of the book is Zar's relationship with his father, which manages the difficult trick of being emotionally moving while remaining true to the depiction of Vulcans. Taken together, it makes for a model of what a Star Trek novel should be, setting a high bar for the many works that followed.