Chapter Text
******
The problem was the voice.
Rocky’s actual voice was music. Elegant shit. Those layered chords were something Grace’s human brain could only admire. But the voice Rocky had chosen… that was the real problem.
Grace had expected something boring. Cheerful, maybe. A little synthetic. The auditory equivalent of a smiling customer-service icon; genderless and featureless, the kind that you heard once in a crowd and forgot the next second you moved on.
Instead, Rocky picked a voice so level, so obscenely controlled that it hit every single one of Grace’s “dangerously hot” buttons.
"Grace," he said for the first time, and Grace forgot what he had been doing for a second. Possibly two. Or three, Whatever. It felt like a warm hand sliding between his legs. Heat rushing straight into his belly before he could stop it.
Then the moment just passed, and he went back to explaining why Eridians liked it hot, why the xenonite could be glued to aluminum and why the sample container was not in fact designed to withstand direct impact from an Eridian claw, blah, blah, blah.
"Grace understand, question?"
"Y-Yeah." Grace cleared his throat."Totally. Got it."
Rocky tapped two claws together. "You did not hear first time."
"I was thinking." He was lying.
All Grace thought was how his name just sounded. From another person. So soft and patient. Like Rocky was tasting it. Like he was already thinking about all the other sounds he could pull out of Grace.
From then on, it only got worse.
“Grace. No.”
“Grace. Come here.”
“Grace.”
Every time the Eridian said his name, his body would clench involuntarily, growing slick and aching for no reason at all.
Every time Rocky spoke, he became aware of it again. And that apparently, was how first contact really began.
Isolation, he blamed isolation.
He had gone too long without another human voice. A real voice, not one of the ship's canned prompts, and Rocky was the only intelligent being within several light-years. It was just pathetic human neediness. A man could probably develop a fetish for a microwave if it kept saying his name like that.
Either Grace was losing his mind, or the Eridian had chosen that voice on purpose.
He started asking stupid questions just to hear it more. He dragged out conversations. He suddenly became fascinated by Eridian metallurgy, music, childhood, architecture, anything. Until one day, the question he’d been circling for weeks finally slipped out:
“So… how do your people reproduce, anyway?”
That was where everything went to hell.
Humans were social animals, with pattern seeking brains to form personal disasters. Grace had one alien friend and one unusually attractive synthetic voice, and he was interested in him. That was just human. Nothing worth being embarrassed about. Plus, the interest was mutual and out in the open. Talking about ways of reproduction was not remotely a crime.
So one peaceful day onboard the Hail Mary, they discussed reproduction. It began harmlessly, just like most catastrophes did.
Rocky was calm like talking about using Astrophage as ship fuel. That should have made the conversation less charged. But as Rocky calmly explained Eridian reproduction, like gametes, ruts, complex mating forms, Grace’s attention just kept drifting to those claws.
Those precise, powerful hands that could repair engines, reshape metal, detect microscopic flaws. He couldn’t stop imagining them on his skin. One claw pinning his thigh open, another slowly parting him, testing how wet he got just for Rocky. Sliding inside him, curling, thrusting, studying every clench and tremble like a fascinating engineering problem.
“…this is all explanation Grace gets,” Rocky finished. “What about human, question?”
The vocoder gave Rocky’s questioning chord a gentle electronic rise. Rocky repeated the question, and he gave Grace a start before Grace could manage to hear the question clearly over the drums in his ears.
"Where are we at?" he asked. "Besides that you Eridians go into a rutting situation every few decades."
"How human ..."Rocky paused, one of his legs bounced on the floor, "Need word."
"Fuck?" Grace hated how his own voice sounded.
"Yes." The Eridian agreed. His voice sounded a bit more pleased to Grace, if that was not coming merely out of his imagination. "How human... fuck, question?"
Grace’s mind short-circuited. He was already soaked, thighs pressed tight together under the table as if that could hide how badly he was turned on.
“How do Grace fuck, question?”
The word sounded almost pleased in that low voice. Or maybe Grace was just losing his mind.
He forced himself to answer like a professional schoolteacher.But his voice kept cracking. His face burned. And all the while, filthy expectations kept flashing through his head.
Rocky’s scorching body heat against his inner thighs. That calm voice ordering him to spread his legs.
“Grace. Let me see.”
By the time the conversation ended, Grace was clenching around nothing, underwear soaked, heart hammering. He barely managed a mumbled goodnight before escaping to his bunk.
There was not going to be a single mention of any concept related to Eridian ruts or human heats tomorrow. Maybe the talk about fucking was a game changer.
What a confusing thought to fall asleep with.
******
Falling asleep with Rocky in his head was probably the reason for Grace's dream.
It was the middle of the night (or the sleeping time), Dr. Grace was lying on his stomach and he pressed his cheek into his pillow (made of spare uniforms).
Limbs, strong and hard, braced over him, body against his back, warm as sunlight. That voice was a hot whisper right in his ear as one of the limbs twisted and reached down and stroked against his inner thigh.
Grace. Grace. Grace. How human fuck?
Grace got a full impression of that heaviness and size. Grace tried to push back against him to feel that stroke again, but he muttered Grace's name like praise and crawled up higher, some of the limbs straddling the human's hips, fixing them at a right angle. The warmth ghosted against Grace's back. Grace couldn't get a decent lungful of air.
He was too heavy and Grace was too turned on. Sensitive, forgotten parts of him blazed to life after years of cruel neglect. Grace scratched his blunt fingernails against the sheets until he felt the burn.
The realization that he was having a dirty dream about Rocky suddenly roused him and he teetered on the edge of waking,but he kept his eyes shut. Half-fascinated, he wanted to see where his human mind took this. After a while, he sank back in.
I will do anything that makes you feel good, Grace. You just have to ask.
Rocky's tone was thoughtful and pleased, the one he sometimes used when he mapped Grace's body with that alien vision. It was like the Eridian could see him through walls and know what he looked like, down to his insides.
Grace twisted his head just to see Rocky's hand braced by his head, beautiful alien marks running along his exoskeleton. He could see a patch of the Eridian's limb. Eridian measurements, clan crests, words, symbols, or tattoos that looked like circuitry etched into marble. That hand folded inward into a fist, and the mere thought of Rocky holding back his full alien strength made Grace's inner walls clench hard.
He couldn't see him. He tried and managed to roll onto his back, the comforter and the sheets beginning to twist him up. He was tangled up in Rocky's limbs. The realization that he was soaking wet hit him all at once as he looked up at the Eridian. He let out a gasp of embarrassment. A brief, amused chord was all the Eridian's reply.
Rocky afraid so. That Eridian didn't sound sorry.
There was so much delicious weight, pressing him down. Limbs and hands. Grace moved against dream-Rocky lazily, feeling him hold back a musical groan, and he realized something shocking.
You want me desperately, Grace.
The words echoed in his head, firm and undeniable. A stroke on the pulse of his neck confirmed the knowledge. It was stronger than attraction. It was a relentless need between them, under the harmless label of friendship, that had never found a true outlet, until now. The sheets were burning hot against Grace's skin.
He felt alien hands sliding along his body, so steady and precise, stripping away his clothes. He was being peeled, inspected. Under eyes that couldn't see, but map. A ghostly caress, his back formed into an impossible arch, and he was being played. Moaning, gasping, sighing, under those careful hands, like a piece of finest instrument finally finding the hands that knew how to play it.
You've known this all along, Grace.
The Eridian whispered against his ear, and the hint of a smile underneath his voice tipped Grace off the edge.
He woke violently, tangled in the sheets, breathing hard. For several confused seconds he did not know where he was. Slowly, the ship resolved around him, clearing the haze, reminding him that Rocky was still somewhere beyond the wall.
Grace lay back, boneless. His clothes clung unpleasantly to his damp skin.
"Oh," he whispered. Then, after peeking beneath the sheets, "Oh, no."
He closed his eyes and sucked in a sharp breath. Dreams dissolved under examination, mercifully. Fragments weren't easy to forget though. The pressure of being held in place, the impossible coordination of multiple hands, Rocky’s voice saying his name with a certainty he used every day living with him... Oh. No time for this anymore. Grace pressed both palms over his face.
“This is fine,” he told the ceiling. He changed his clothes, cleaned himself up in the dormitory's bathroom with a swipe of sponge, and was determined to spend the following morning avoiding his other roommate in a spaceship as crowded as the Hail Mary.
******
It was absurd. Grace knew it was.
Rocky was an alien engineer shaped like a large stone spider built from basalt and granite. He breathed ammonia that could melt Grace's lungs. He liked it hot and his body temperature was high enough to be medically alarming. And yet Grace wanted him anyway.
Maybe he just wanted closeness. Any closeness.
If Grace couldn't name how he wanted Rocky, that explanation would still be available. But at night, when the ship went quiet and there was nothing left to distract him, all excuses burned away.
Grace thought about Rocky’s hands. The careful pressure of his claws. The unnerving possibility of being studied with his full attention. He wanted that calm, level synthetic voice saying his name, repeatedly, softly. Being treated like he was the only problem worth the Eridian engineer to solve slowly.
And Grace’s control failed a little faster. He lay on his back in the dark, blanket pulled up over his waist. His hand slid down slowly at first, tentatively, settled between his thighs. His fingers brushed over where the heat was.
Rocky would be resting in his bedroom, unconscious enough that Grace could enjoy a moment of privacy. He lay on his back beneath the blanket, staring into darkness.
He was wet. Embarrassing, shamefully wet.
He touched himself cautiously at first, fingertips circling his clit through the pants while maintaining the determination to think about nobody in particular. This failed immediately, because Rocky appeared in his mind when he rubbed himself again.
Grace.
His breathing caught. His body clenched around nothing, and fresh wetness gathered beneath his fingers. He tried replacing the image with something human. Something from Earth. A face. A body he knew. A person who touched with five fingers, had tolerable body temperature and soft skin. It was useless. Rocky returned with infuriating ease.
He pulled his pants to the side, the moment two fingers parted his damp folds and sank inside, the thought of his Eridian roommate became unbearable.
Those careful claws moving along his body, capable of both brutal strength and terrible gentleness. There was one claw pinning his thigh open, the other gently exploring his slick, feeling him, studying him.
Grace's breath hitched. His fingers curled deeper, moving with a steady rhythm while his thumb circled his swollen clit.
Grace bit down on the inside of his cheek. Be quiet. You have to be quiet.
He knew this.
Grace slowed, waited for his breathing to settle, then continued. But the fantasy became became out of control. Rocky’s hands. Rocky leaning close. The vocoder speaking in that impossible voice and tic tic tic when the Eridian was excited.
Grace. Come here.
Let me see how wet you get for me.
A broken whimper escaped. Grace touched himself faster, two fingers deep inside his tight heat, and the slick was dripping down to his knuckles. His free hand curled in the blanket, seeking for purchase, as his hips rolled up. He imagined Rocky studying every reaction, asking questions with unbearable seriousness.
Good, question?
Grace swallowed a sound.
Grace feel good, question?
"Yes, mmmpf fudge--" he gasped before he could stop himself. "Please--"
He was soaking the sheets now, clenching around his fingers. The pleasure built up inhumanly fast. He paused and resumed, faster now, too far gone to maintain the fiction that this was impersonal. In his mind, Rocky's voice dropped to that impossibly gentle register:
Grace. Do not stop. You may finish now.
The pressure broke through him abruptly. His back arched violently, cunt gripping hard as a gush of slick flooding over his hand. The orgasm slammed into him, harder than ever was. Grace had never experienced that kind of pleasure before, it was the hardest orgasm in his life.
"R-Rocky--"
The name left his throat before he understood he was saying it.
******
Rocky first noticed the sound at 03:17 ship time.
He didn't really sleep. Eridians entered periods of reduced activity, but they did not become deaf, blind, or--he had recently learned the exact human phrase for it-- socially excused from everything that happened nearby. Humans, by contrast, became unconscious for several hours and apparently regarded this as both medically necessary and completely normal.
Grace was especially committed to the practice lately. He slept in a narrow bunk on the other side of the ship, enclosed in breathable atmosphere and surrounded by enough soft material to suggest that humans had never fully accepted the invention of a hard surface. Rocky had built him a better mattress three weeks earlier on a whim. Grace complained that it was too firm, then admitted after two nights that his back no longer hurt.
Resistance, experimental testing, reluctant surrender to evidence, this was how Grace expressed his gratitude to his sole alien companion aboard the ship. Strange, but Rocky liked this about him.
Since the day they met, Rocky had developed a frankly excessive curiosity about trivial human things. And curiosity wasn't quite the right word; he was fascinated by Grace, though Rocky hadn't yet examined why.
Rocky's senses stayed sharp, especially when it came to Grace. At 03:17, Grace’s heartbeat had accelerated.
Rocky perked up and lifted his attention toward the sound, all five limbs folded loosely beneath him. The change alone was not alarming; human heart rates were noisy, erratic instruments. They accelerated during exercise, fear, excitement, arguments, strong coffee, mild coffee, and once while Grace had been looking at a photograph of a sandwich.
Normally Rocky would call through the wall with a "what is Grace doing, question?" and secretly enjoy the human groans made by the only human he had ever known.
Being an intrusive alien roommate was usually enjoyable. But this time, Rocky listened. For a reason he couldn't quite put a claw on.
The ship carried sound well around the night. With the engines quiet and most systems running at reduced power, every vibration went through the walls. The ventilation fans, the faint cycling of pumps, the small adjustments of cooling metal.
And, of course, Grace.
The human's breathing pattern had changed.
Not the broken, high-pitched pattern of a nightmare, no. Rocky knew that all too well. It had occurred on a couple of nights when things weren't going well, so he learned it over time. Not that Eridians didn't dream, but his own kind rarely acted that violently in a dream state.
Grace had objected the first time Rocky woke him up by tapping his bulkhead hard. It came off harder than intended, the force Rocky used in it even dislodged a storage container above him and nearly dropped it onto his back. But that was nothing compared with Grace waking up and admitting, softly that he was glad Rocky had done it. Ah, Rocky would love to do it again.
But this, this was different...somehow.
This was slow at first, then uneven. Carefully controlled yet repeatedly broken. The bunk creaked under him, a mechanical complaint. Rocky shifted slightly on his limbs and listened, with growing interest.
There was another movement and the fabric shifting. Then, a bitten-off exhale through Grace’s nose, hovering between sigh and moan. A soft, wet sound. Skin sliding through slick flesh. Normally the sound made by human fluid would make Rocky feel gross, now it struck him in a strange way.
Rocky mapped the vibrations without intending to, like a primal instinct. That could probably violate two or three of their roommate rules, but at this point Rocky couldn't care less. Still, no sign of distress. Nope. Okay. So what could be the problem?
He mapped the surroundings again, for possible hazards, just to make sure.
Grace lay on his back, one arm bent near his head, the other moving beneath the blanket in a small, repetitive rhythm. Fingers thrusting. Rubbing. The wet sounds were unmistakable now.
Oh.
Oh.
Understanding hit him like a spacecraft.
Grace had explained human reproductive behavior days ago, during one of their less dignified scientific discussions. Well, in that matter, Rocky had learned enough.
Now, through walls and several meters of ship, he heard Grace performing it all alone.
He should have disengaged, or returned to his project. But... but Grace was doing unusual things. That was a technical reason, and therefore a respectable one. He had monitored unusual situations for their safety and the Hail Mary was a fragile environment, and Grace was a fragile organism occupying it. Rocky wanted to stay awake for Grace.
The bunk creaked again, louder this time, followed by a small frustrated whimper from Grace. Rocky had heard him make similar sounds while trying to fix things with the wrong tool. No. Stop. This comparison wasn't helpful.
He moved closer instead, shifting himself for better receive. The slick sounds of Grace's fingers moving in and out himself. The little moans he tried to swallow. A strange, burning heat bloomed deep in Rocky's central mass, spreading outward in pulsing waves. His claws flexed. His carapace felt too tight.
He wanted to tap the wall. Wanted to ask: Grace, what are you doing, question? Grace, do you need help, question?
All those lovely human noises would come to a stop.
He liked to watch Grace lost in pleasure, and he also liked the idea that he could easily make this human stop and turn to him whenever he wanted.
Grace would hold his breath, bite back his small moans, and clumsily pull the blanket higher over his bare chest, and give Rocky his full, flustered attention again. He would answer in a voice hoarser than usual: "what happened?" Like he didn't know he was the reason.
Just the thought sent a pleasant buzz through Rocky's body.
After a few halting attempts, Rocky lifted one hand toward the wall. He just couldn't resist it.
During waking hours, Grace filled silence automatically. Explaining, joking, whining, revising his whining, making jokes about his whining, and then explaining why the joke had been funny. He was never quiet unless exhausted or distraught. Here, in the dark, there was none of Grace's usual noise anymore. Here,just him and his moaning and he was so gone he never took the observer in the other room into his account. Probably wouldn't even remember this when he woke up hours later. Grace would never know he was listening, anyway.
In this moment, they were so intimate, more than they ever had. So strange. And beautiful. Space was so vast and empty and unbearable for so many years.
The expected knock never came. The Eridian stayed silent. Because listening to Grace like this... was intoxicating.
Then, unexpectedly, he heard a word before he understood it.
"R-Rocky--"
Soft, trembling. Dripping with desperate need. Nothing like the usual exasperated way Grace said it.
Grace’s mouth shaped it tenderly, the first syllable blurred by breath, the second almost lost in a moan. The Eridian registered it despite himself.
Rocky froze completely. A bright fire traveled through him, hotter than his own core temperature. His body thrummed with a low, pleased vibration.
That wasn't for him, for sure. He was walls away. Grace could never know he was listening, human senses were nothing compared with an Eridian's, and that was the only reason that his name in human form sounded like that, all soft and intimate.
Grace said it again, voice cracking into a whimper as his rhythm turned sloppy and frantic.
"Rocky... fuck--"
Rocky shifted again, a low vibration rolling through him. An Eridian purr that no human ear would catch. He pressed a hand against the cold metal, imagining the slick heat fluttering around those fingers, the way Grace's body would feel-- it was likely soft, scalding, and soaking wet. He was curious about how would it really feel.
He liked this far, far too much.
That should have been the first warning.