When Robert Wise’s “Star Trek: The Motion Picture” beamed into theaters on December 7, 1979, it was a gift to the fanbase that had grown up around “The Original Series” after NBC canceled it in 1969, and a cordial invitation to everyone else to join the voyages of the Starship Enterprise. When the $44 million film grossed a disappointing $83 million in the United States, the future of “Star Trek” was once again uncertain.

The issue with Wise’s film is that it was too reverent in tone and, for newcomers, staid in comparison to the lightsabers-and-blasters derring-do of “Star Wars.” Perhaps most damaging of all, it didn’t naturally lead to a sequel. Where was “Star Trek” to boldly go from this tepidly received epic (which has found its vociferous defenders over the years)?

The unexpected answer was to blend Gene Roddenberry’s socially conscious sci-fi saga with naval warfare yarns like Patrick O’Brian Aubrey and Maturin’s series of books, and submarine movies like “Run Silent, Run Deep” and “The Enemy Within.” Throw in a director who wasn’t a fan of the show (Nicholas Meyer), and you end up with the masterful “Star Trek II: The Wrath of Khan.” Released during that magical summer of 1982, Meyer’s movie made $80 million in the U.S. on a far more manageable budget of $12 million and remains the franchise’s feature gold standard 43 years after its release.

But “Star Trek II: The Wrath of Khan” was not without its risks. In killing off Leonard Nimoy’s Spock, the franchise was suddenly looking at a future without its most beloved character. This was, of course, unthinkable, which is why the next movie, “Star Trek III: The Search for Spock,” was all about rescuing the character from the unstable planet Genesis. And yet the most interesting development in Spock’s life was conceived before his death in the second movie. Had all gone according to the franchise’s new plan, Saavik, Spock’s Vulcan protégé, was supposed to be pregnant with his child, which would’ve been revealed in “Star Trek IV: The Voyage Home.” Why didn’t this come to pass?

As introduced in “Star Trek II: The Wrath of Khan,” Saavik (Kirstie Alley) is a sharp pupil who’s particularly interested in how Captain James T. Kirk (William Shatner) eked out an impossible victory when faced with the no-win Kobayashi Maru scenario during his schooling at Starfleet Academy. We’re immediately intrigued by her because she’s not buying Kirk’s prevarication, and, well, Alley is just a naturally captivating actor. Saavik is a character with potential, and when Spock is killed (a moment that brings her to tears), she seems to be his natural Vulcan heir on the bridge of the Enterprise.

“Star Trek III: The Search for Spock” unsurprisingly thrusts Saavik right back into the action alongside the other young character introduced in the previous movie, Kirk’s son David Marcus (Merritt Butrick), but the dynamic is off because, due to the studio’s refusal to meet Alley’s reasonable contract demands, Saavik is now being portrayed by the considerably less compelling Robin Curtis. At the time, the recasting served to relegate Saavik; David briefly stepped to the fore (until he got fatally stabbed by a Klingon), and Saavik felt like an afterthought by the end of the movie. With Spock back in the rotation, what was to be done with Saavik?

There was a plan, and it’s probably for the best that the “Star Trek” braintrust at the time scrapped it.

At the outset of “Star Trek IV: The Voyage Home,” Saavik makes the curious decision to stay on Vulcan. She’s a fast-rising officer in Starfleet who’d earned an unimpeachable mentor in Spock. Why would she hang back on her home planet when she’s only distinguished herself under the questionable supervision of Kirk?

The answer is that she is about to bear Spock’s child.

That’s a lot to spring on an audience regardless of their familiarity with “Star Trek.” Given what we know of “Star Trek IV: The Voyage Home,” the top-grossing film featuring “The Original Series” characters, it’s impossible to imagine the director integrating this weighty plotline into a lighthearted time-travel romp – especially when that director was Spock himself, Leonard Nimoy (with strict input from William Shatner).

On the audio commentary for the Director’s Cut DVD of “Star Trek IV: The Voyage Home,” Nimoy said that it was more intriguing to leave Saavik on Vulcan “with the potential information that she was expecting Spock’s child.” Producer Harve Bennett later said Nimoy was never comfortable with pursuing this plotline for Spock — which would’ve been a lot to throw on the character after he’s just been resurrected.

Ultimately, the Spock-Saavik arc was cut completely. While this was the right decision, it led to the egregiously awful choice to give up on Saavik altogether. “Star Trek IV: The Voyage Home” repped the character’s final appearance; as far as we know, she stayed on Vulcan and led an unremarkable life. It’s a depressing betrayal of a character who possessed such amazing promise, and, to date, “Star Trek” has not expressed much interest in bringing her back.