Nineteen dead.

Among them, Chekov and Carol.

Bones has wrapped a tourniquet around his shoulder until the casualties can be triaged.

He'd tried to follow as Bones and Scotty walked past him, faces grim and set, bracing themselves to identify the dead.

"Jim, you've got a gaping shoulder wound and a concussion. Just sit still."

And so he watches numbly as Chekhov is lifted onto a black stretcher, as Bones takes Carol's pulse and his face falls, twisting for a second in despair.

Uhura is being stretchered towards the infirmary, Spock beside her. He's still bleeding, a hand pressed against his side, and Kirk realises that Bones has not noticed.

"Spock," he starts, lurching towards him. "Is she okay?"

"I believe so," Spock says after a moment, and his voice is steady but Kirk has seen that look in his eyes before, and aches. "She was conscious. I need to go with her to the infirmary to establish–"

"You need to get stitched up before you go anywhere," Kirk says, relieved at the chance to lead again. "Just wait for Bones. Please."

Spock doesn't protest, his gaze fixed suddenly on a point somewhere beyond Kirk, and he turns.

Khan is standing against the wall, watching the proceedings with no apparent reaction. Spock, on the other hand, has rarely looked more vicious.

"Why are you here?" he asks, voice low.

"You have more urgent concerns, Mr Spock."

"I must disagree. The timing of your arrival, coinciding as it did with that of the Klingon battalion, is among the most pressing of my current concerns."

"What are you suggesting?"

"I am suggesting that this is not the first time you have joined forces with the Klingons," Spock says steadily, advancing towards Khan with eyes dark.

"And what do you imagine either I or the Klingons would stand to gain from a plan that involved me single-handedly laying waste to their army?"

"I don't pretend to understand what motivates a mind like yours. But I can understand how it might be beneficial to ingratiate yourself with this crew by appearing to provide timely rescue."

"Oh, yes," Khan drawls. "I regained the trust of the Klingons – whose ranks I decimated once before mere weeks ago on Kronos, as you will both recall – enlisted them to attack this ship, and threw myself headlong into battle with them while you all cowered behind me. All this, I did solely to gain your hard-won approval. Does that sound logical to you, Mr Spock?"

"Why, then, did you help us?"

"More to the point, how the hell did you get on the ship?" Kirk asks.

"It was less of a challenge than you might like to think, Captain. Security measures are curiously lax if one knows the right cargo entrance to watch."

"You were inside a cryo-pod. Sealed. At Starfleet."

Khan doesn't answer, and suddenly Kirk realises he doesn't especially care. So he escaped. Sure. Why not?

From the corner of his eye, he sees Carol zipped into a body bag. He puts his head in his hands, nausea coming in trembling waves.

"So you claim you were unaware that the Klingon attack was coming?" Spock asks from somewhere above him.

"You and your employers might be too arrogant to imagine that war could possibly come unless you yourselves declared it. But I've known ever since Kronos that there would be consequences," Khan says. "I had no prior knowledge of the specific attack. That it came today was merely convenient."

He hears a scuffing sound, a dull thud, and when he looks up Spock has Khan in a Vulcan nerve pinch against the wall, choking him with the other hand.

"You would be unwise to describe the events of today in those terms again," he snarls, and as Khan yells out in pain Kirk wonders at what has been unleashed in Spock, so swiftly.

"Spock," he tries weakly, concerned for the wound still bleeding steadily from below his ribs.

But Khan recovers, delivering a sucker punch to Spock's injured side and as Spock crumples, Khan doesn't let him fall.

"Kirk," he bites out, holding Spock up with one hand. "Attend to your first officer, if you would."

But before Kirk can get upright Bones is there, shoving Khan viciously back and guiding Spock down to the floor.

"Damnit, you could have mentioned this earlier," he mutters as he tears open his uniform, exposing charred skin, and Spock is unresponsive. The blood loss has finally taken him.

Kirk watches Bones work, green blood dripping over his hands, caught in the gaze. He needs to do something. Lead. If only his goddamn head would stop spinning long enough for him to stand up properly.

"Sir? What do you want done with the prisoner?"

He looks round.

Four officers have Khan handcuffed between them, and a fifth is looking expectantly down at Kirk.

"Take him back to the holding cell, for now."

He's back on Spock's blood, watching it pool slower and slower as Bones stitches his wound with deft, precise movements, his hands perfectly steadily.

The blood.

Jesus, he hasn't been thinking.

"Wait," he shouts, and the officers pause at the doorway, Khan halting first almost as though he knew the order was coming.

"Sir?"

"His blood," Kirk says, his own voice loud in his ears as he moves over to them. "His blood, it can bring them back. Everyone. None of this–" and he's laughing, suddenly, hysteria and so, so much relief, "none of this happened. We can bring them back."

There's silence, all five officers looking blankly at him and do they not know? Maybe not.

"Bones, how much of his blood did it take to bring me back?"

"Little under two pints in a transfusion," Bones answers, voice tight, eyes still fixed on his work.

"So, okay, so that's six people right there," Kirk calculates, ten to twelve pints of blood in the average human, yes, he knows this, this will work, "and he must regenerate blood cells way faster than normal, it's not like we're gonna have to wait long."

He turns wildly, sees Scotty in the distance looking sick, struggling with the zip on another body bag.

"Scotty, it's okay! Just… all we need to do is keep them cold, for the next few hours, just preserve them and we can bring them back. We can bring them back," he repeats, a mantra, yes yes yes.

"No. You can't."

"We're not giving you a choice," Kirk snaps.

"I am not referring to my own resistance. My blood will not bring back your fallen crew."

Khan's voice is like a lead weight in his stomach, dragging.

"What, you don't have enough? Fuck you, you're indestructible, you can't replenish your own blood cells?"

"You could drain me dry a hundred times over and it would not bring them back," Khan says, his voice utterly flat.

There's bile rising in his throat.

"You're lying."

Khan rolls up his sleeve, extends his arm.

"You're more than welcome to try."

Before Kirk can respond, Bones is at his elbow.

"I can't do this here. I need him hooked up to a blood bag."

And already he's shepherding the five officers and Khan out of the wrecked bridge, towards the infirmary and Kirk is left to trail behind, repeating the same thought to himself over and over because nothing else makes sense.

This will work.