Just a tag to the story, in case the ending was too morbid for ya.
He wakes up in Sickbay some indeterminate time later- early morning, by Enterprise's chronometer – and the lights are still down, the little curtained-off areas quiet without the bustle of daytime personnel.
"Mattie." Someone says quietly, and it takes Jim's fuzzy brain a moment to realize it's Scotty. The world comes rushing back to him in an instant; the cave, flashbacks, Pavel's screams, the blood – reflexively, Jim looks down at his hands, expecting to see or feel that awful slick of red, and is surprised when there's nothing but his own smooth skin.
"Matvei is a good name." a soft voice insists.
"Aye, but it'll get him nowt but trouble on a playground. Mattie's fine, darlin', for a nickname. Mattie Scott."
"Matvei Pavlovich Scott." The weak voice repeats, and Jim sits up so fast his biobed starts making all kinds of worried noises. Before a nurse can accost him, though, his bare feet hit the floor and he's stepping through the thin white curtain beside him.
"Captain!" They say at the same time, and the accents create an unintelligible dissonance, but he doesn't give a damn because there's Scott holding Chekov, who's cradling the baby and mid-way through stroking one of his tiny curls. Pavel's white-pale, and Jim can see the bulk of bandages and stabilizers under the boy's hospital gown, but his eyes are open and he's alive.
Jim's weak with relief, and sinks into the chair beside Pavel's bed smiling like an idiot and near to tears at the scene of this tiny, miraculous family.
"How- I thought, I mean, when-?"
Scotty seems to understand what Jim's asking, and nods. "Aye. We all saw so much blood – the Doc, he couldn't find a pulse, 'twas so weak – and when I saw Sulu's face, I thought the worst." He takes a long look at Chekov, as if reminding himself that it wasn't real, and goes on, "The surgery took a good seven hours. But McCoy pulled it off, the miracle worker."
"I'm a doctor, not a miracle worker." A sleepy voice grumbles, and the doctor pokes his head around the curtain, "Jim, get back in bed. You've got a crack in that thick head of yours, damn fool."
"Is that how you talk to the Captain?" Jim shoots back.
"It's how I talk to morons who don't give their own skull a chance to heal." Bones says with good-natured grumbling, and even as he shoves Jim back towards his bed he can tell the Doctor is riding the same wave of relief. "And you, Scott, give that boy a rest-"
"Aye aye, sir." Scotty drops a gentle kiss to Pavel's forehead, and rises carefully from the bed, tucking blankets around him. "Back to sleep wi' you, darlin'. We'll be here later today, alright?"
"Da, Mory." Pavel replies, and kisses his son with a soft sigh of contentment, and Scotty with a note of longing. The two of them stare into each other's faces for a long moment before they separate. Jim realizes, in a distracted flash, that there are exactly eighteen years between Scott and Chekov, and the same distance between Pavel and Matvei; something circular about it pleases him, or at least makes him want to tell Spock about the observation.
Scotty takes the baby carefully, handling Matvei even more gently than Jim's seen him hold engine components and delicate circuits, and heads out with one last, grateful look at Pavel. The boy's already beginning to drift off, but he manages a soft "Spasiba, Captain. For everything." that Jim receives with a silent nod.
McCoy herds Jim back around the curtain and up onto the biobed, which picks up recording his vitals. The doctor inspects one of the read-outs intently, checking it against some earlier figure.
"What's the damage report, Bones?" Jim asks. He can feel the place where his head was gashed; the skin on it is tender and sensitive, surely regenerated.
"Hairline fracture, but you were developing a hematoma. M'Benga did a good job. Don't mess up his work with a lot of jumping around." McCoy says gruffly.
"And Chekov?" Jim asks, more hesitantly. Even in the dim light, he can see Bones' wince.
"It was bad. I've never seen a birth go that…" he trails off, caught in the memory of what must've been a pretty horrific surgery. "The kid was all ripped up. He was small to begin with, and these pregnancies are always risky if you don't get the hormones finished right. Chekov'll be alright, but he's never going to have more children. I don't want him on any away missions, either, for the next few months. Maybe longer. That was a damn close call."
"But the baby's healthy?"
Bones adjusts something on the panel above Jim's head, and nods with a smile blooming on his face. "On the small side, but fine. Looks a lot like Chekov, with Scott's freckles. You did a good job, Jim."
"I thought – at first, he wouldn't breathe, and I about lost it, Bones." He admits in a voice so small it's almost non-existent.
The doctor goes quiet, fiddles a bit more with the controls on the biobed, and eventually he perches on the side of Jim's bed. "You did, a bit, kiddo. As we were clearing off that layer of rock- you were screaming your head off, Jim. I think most people assumed you were trying to make us hear where you were."
"I was- I remembered something. It was like before." Jim has to force the word out, "Tarsus. I was hiding, and she – she'd been hit a while ago, and it happened really fast, but I couldn't move from inside the wall…"
"Hoshi Sato." Bones says softly. When Jim nods, he adds, "You said something to Spock. He checked the name."
"She- she knew my mom, from way back. Taught me Japanese. We hid together, for a while."
Bones is silent for a long time, and just as Jim begins to drift towards sleep he whispers, "I'm sorry, kid. Must've been hell in there."
"Was more worried about Chekov. Couldn't waste time on remembering." He mumbles, fighting to keep his eyes open.
"I know. You did the right things, though, Jim. Got 'em both home safe."
"Yeah?" Jim asks wearily and a little searchingly, feeling himself sliding deeper into a bone-weary sleep.
"Yeah, you did. Just fine." Bones murmurs, and it's enough to let Jim's eyes drop closed, let himself sink into rest, with the soft sound of Pavel's even breathing a few feet away and a warm hand on his forehead.