I've always thought the 'resolution' to the Horta episode was sort of horrifying, so this is me exploring that concept a little. It's also inspired by a song I just found, 'Demon in the Dark', which can be found on youtube. It has all the Horta-feels. And yes, that is a thing.
watch?v=k3a-H98caPQ
It is the duty of the Newest Mother to watch the Vault, and the Future within the fault. For generations this tradition has been unbroken, passed from youngest child to youngest child. The Newest Mother is the keeper of a hundred thousand sisters and brothers and cousins, and even some who are children-by-birth, her own beloved.
She senses the sparks of their minds from the coolness of the deep places. There are no predators on this world, and there have been none for a hundred thousand years, since two New Mothers before her. She must simply wait for the Long Sleep to finish, and though she mourns for her lost kin, who sacrificed themselves to the earth so that the Future might survive, she eagerly awaits the children. Her children.
They are stirring in the eggs. The Future dawns soon.
"Are you alright, Spock?"
Spock looks up; he seems almost startled, though Kirk is unsure if this is due to his question. Spock has been staring at the chessboard for a full four minutes in silence, and Kirk is starting to suspect that the Vulcan has drifted off into his own thoughts.
"I am fine, Captain," Spock finally says. The odd emphasis makes Kirk frown.
"You're sure?" He presses.
Spock looks at the chessboard. He is losing the match. With a sharp, sudden movement, he reached out and tips over his king. "I need to meditate," he says abruptly, and stands. Surprised, Kirk rises with him, but Spock is already walking away. "Goodnight," adds Spock absently, and the door slides open.
"Goodnight," says Kirk, bemused, to the closed door. He sits down in the silent quarters. "I wonder what that was about?"
There are sounds rising from the surface, odd creatures drilling down into the caves. They are peaceful. They do no know of the Horta, or the Newest Mother. But they drill down, down, down, and while she can flee farther downward the Vault cannot be moved.
Not all the children are in the Vault; some mothers in their last throes of death left their eggs outside, and these cannot be moved. The Newest Mother circles the caves, but for now, she will wait.
Kirk knows that Spock sometimes has these moods, much as the reserved scientist would object to the very thought of his behavior altering due to random emotional shifts. So Kirk never mentions his occasional odd behavior, and usually it passes within a day or two. But they have been back in space a week, and he still catches Spock staring into the distance. The first officer has turned down all offers of chess or sparring, and by all accounts has hidden away in his rooms the past few evenings, doing god only knows what. Even McCoy has commented that "Your Vulcan needs to get out more, Jim - he's making the ensigns nervous."
So when he catches sight of Spock off-duty in the mess hall he waves the Vulcan over so blatantly that it would be an insult if Spock were to ignore him. Stiffly, Spock walks over and carefully takes a seat across from Kirk.
The captain pauses, waiting to see if Spock will speak. The Vulcan bows his head over his food and starts to eat in silence.
Not a patient man, Kirk clears his throat after only a minute or two. "Spock, I feel that our last conversation didn't exactly... end."
He half-expects Spock to prevaricate. To say, 'Our last conversation, captain, occurred on the bridge, and concerned the upcoming shore leave on Beta Thoranus XII. May I ask how it is unresolved?'. Or perhaps he will change the subject entirely, or make some pointed comment about an obscure Vulcan habit of eating in total silence. Spock is very good at playing obtuse when he wants to, and he always wants to when Kirk tries to bring up anything personal.
So therefore he is surprised when Spock simply says, "I agree."
Kirk waits, because even Spock can't say something like that and then change the subject. Not that he would put it past his friend; for a Vulcan, a race that is practical and supposedly ready to accept reality as-is, Spock is curiously defensive about anything to do with himself.
"What are your thoughts on our last mission, Captain?"
The soft question brings Kirk out of his reverie. "Janus VI?" It has, after all, been nearly a week. "We were - lucky, I suppose."
"Lucky," Spock echoes. His voice is flat.
"There was one casualty, but it could have been much worse. And the misunderstanding was cleared up peacefully."
"Peacefully," Spock repeats again. "Misunderstanding."
Kirk frowns. "Is something about the mission bothering you?"
Spock looks at him.
"If this is about your... mind meld," he begins, and Spock straightens, "McCoy and I know that - what happened - was a result of the meld. There's no need to be..." Embarrassed - " - awkward."
Spock's face is inscrutable. He examines Kirk for a long, uncomfortable moment, and then rises. "If you will excuse me," he says icily, and without waiting for a response he stalks away to discard his untouched tray and exit.
The lights in her mind flare and die one by one, and with each dead child she feels her race slip one step closer to extinction. She is the Newest Mother, and meant to guard the Future, but it is possible that she will also be the Last Mother.
She weeps tears that burn through the stone of the high caves, and these tears burn down and touch an intruder. He yelps and shrieks, flinching back from his tools, and then stops moving. The intrusion into the caves stop. He is silent.
She does not want to kill. This race does not deserve extinction either. But the children are so close to Becoming. The Future cannot be lost.
Perhaps if she can stall them with her own life, at least one egg will be able to hatch, and she will not be the Last.
Kirk presses in past Spock to enter the first officer's quarters, exasperated. Enough is enough.
"Sit down, Mister. This is getting ridiculous."
"Sir - "
"Sit."
Spock sits.
Kirk paces for a moment, reminding himself that getting annoyed will solve nothing. When he feels in control, he asks, "What's bothering you so much about the Janus mission, Spock? It was ended to everyone's satisfaction - "
Spock clenches his fist, inhaling sharply. Kirk stops pacing and stares. Though the Vulcan's face did not change, that was clearly an indication of emotion. Kirk is amazed. "What is it, Spock?"
"There is no peace. There is a tragedy that no one wants to acknowledge, and now the Horta are blackmailed into working for the Federation - "
"Blackmailed! Spock, the Horta were perfectly willing to share the planet and work with the miners - "
"But they should not have to. It is their planet. Starfleet is entirely ignoring the Prime Directive - "
"There's no point in leaving now that they already know of our existence - "
"I am not finished!" Spock snaps.
Startled, Kirk falls silent.
The Vulcan pauses, taking a slow, careful breath and smoothing his features. When he speaks again his voice is slow and careful. "Captain. The Horta are unlike any species we have encountered. But they are intelligent as either of us, and possess the same capacity for emotion." Kirk looks at him in amazement, which Spock ignores. "I would have you consider, for a moment, walking into this situation. A humanoid female, if you prefer, very young, is surrounded by the broken corpses of her children. After brutally and unrepentantly murdering thousands of her young, in a move which surely can only be the act of a savage and callous race, she is given the proposition of assisting this race in their endeavors in exchange, as you so eloquently put it on the planet, for the promise for each species to 'leave the other alone'."
Kirk is staring at him, slow horror coming over his face, as Spock continues. "Mr. Vanderburg spoke, with some distaste, of the possibility of, to quote, 'thousands of those things' crawling over the planet's surface. Those things, captain, are sentient lifeforms, and we have stolen their birthright; not to mention the lives of a substantial number of their siblings. I can think of no other term to describe the mission than one of a very ugly type of coercion. The fact that the Horta are not shaped or made in any way familiar to us does not mean that they are less due the same respect given to any sentient lifeform, and I cannot in good conscience condone our course of action on Janus VI."
Kirk stares into the distance, very pale, and Spock gives him a moment to digest these words. Finally the captain speaks, as though just for a way to stall: "Why didn't you say anything on the planet?"
"I wrote as much in my official report. However, directly following the mind-meld I tried to dismiss such considerations. I thought it possible my opinion was influenced by my encounter with the mother Horta. And while that may be so, I have determined that this possibility does not invalidate that opinion. The mother Horta was deep in grief. She would have agreed to anything that was so long as we might allow her children to live."
Kirk closes his eyes. "Sometimes, Spock, I think we're not ready for this. For any of it. Too eager, too arrogant, too selfish..."
Spock says nothing.
"...I'll contact Starfleet. Advise them to consider what you've said, and to get a team of telepaths out there to begin proper relations with the Horta... and to offer reparations."
"I believe that would be best."
"And Spock - thank you, for telling me this. I needed to hear it. And the Horta needed it to be said."
The children are dead. So many dead, so many splintered and dying, crying out with their minds, and she is helpless. She is a failure, and as she hurts and struggles to move she can only hope that she will die before the last of her children. No Mother should watch her children die.
But there is a new intruder, and this one is different. He has a mind-touch of his own, alien but bright. He reaches. He understands. And when he Sees through her eyes and looks at the broken, shattered bodies of her children, he mourns.
Perhaps the Future is not lost.