So far, the whole 'five-year exploration' thing is working out exactly as Kirk hoped.

When he'd committed to the mission, he'd never admitted that the main reason it appealed to him was its relative safety. Near death experiences were one thing; those he could coast through on adrenalin and turn into killer anecdotes to tell over a beer. Actual death, as it turned out, had been less easy to shake off.

He'd never admit it. And he's choosing to believe that his crew don't know it, although Spock's gaze lingers on him for just a little too long now and Uhura's gentle with him in a way she never used to be and Bones is always naming some new reason to check him over in the infirmary.

He fakes it as hard as he can, does the whole gung-ho smirk thing and flirts ostentatiously with Carol and keeps his hands steady, absolutely steady, even when he walks through Engineering and sees the radiation chamber, that glass pane, hears the warp core thrumming within.

This has made him hate the heart of his own ship, and that just might be the worst part of it.

Still, the mission has been going smoothly. The first week they'd landed on what appeared to be an uninhabited planet, and discovered some kind of micro-organism that made Spock about as outwardly excited as was possible.

It hasn't been thrilling but it's been exactly the break he wanted, and when he wakes up shuddering now, he can force himself to relax by mentally recounting the logs from their exploratory missions to date, the findings, the planet coordinates. And it helps.

Things have been good.

Until today.

The first sign that something is wrong is a low whining noise somewhere overhead, so low he thinks he could be imagining things. Bones still has him on a litany of meds, which he mostly remembers to take.

"Do you hear that?" he asks Chekhov, who's squinting intently at his monitor.

"What, captain?"

"That–"

Abruptly, the lights go out. The bridge is plunged into darkness, possibly the entire ship along with it and that just shouldn't be possible, he's thinking to himself, the backup systems should have kicked in the same instant the power failed.

"Mr Scott!" he shouts, stabbing at his comm. "What the hell is going on down here?"

The monitors have all gone dead, too. They are flying blind. There's no response from Scotty.

"Well, this is just great," he mutters, as panicked voices grow gradually louder around him. "Okay, everyone, stay calm, this is probably–"

Before he can finish the sentence, he's thrown forwards by a blast that rips through the wall behind him, taking out an entire section of controls. Grenade fire, he recognizes, even as his cheek connects hard with the floor.

"Jesus Christ," he mutters, and reaches blindly for his phaser, tasting his own blood.

Through the darkness he can make out a group of stocky figures now, twenty at least, and something in his bones identifies them before his brain catches up, a chill moving down his spine.

He throws himself sideways as another blast hits, and he's winded as he lands, head spinning. Get on your feet, he thinks, and staggers upward but his legs are like jelly and won't hold him. Behind him, he hears someone screaming over and over again, a siren rhythm.

The Klingons are advancing, and he fires clumsily into the darkness, ducking behind a console for cover. He can't bring himself to look down, knows there's a body at his five o'clock and he can't. He can't.

He fires again and one of the Klingons drops. Three more have been taken out by somebody he can't see firing from the opposite side, but there are so many more than he realized, Jesus, they brought an army. Turns out there really are consequences to walking into Klingon airspace and leaving a body count behind you.

A gun blast lands just shy of his head and he ducks down, trying desperately to run a mental inventory, who else was on the bridge? How many?

"SPOCK," he yells hoarsely, seeing a flash of blue somewhere ahead, but there's no reply and now four Klingons are bearing down on him, suddenly, hissing angry clipped words he doesn't understand.

He raises his phaser, manages to hit one before another fires and hits him in the shoulder. The joint explodes with white-hot pain, and he's not even sure if he's screaming out loud, the air is so full of smoke and noise.

One of the Klingons is picking him up by the neck now, and God just let it be over, just do it. But it seems intent on telling Kirk exactly why he's about to die, even as his vision's turning grey around the edges and all he can hear is buzzing in his ears.

His airways are closing up entirely now, unnaturally strong fingers crushing his windpipe and he can't breathe at all. He'd almost drowned once, reckless in white-water rapids during a family vacation in California, and he wonders dimly if choking to death will feel the same, the slow weight descending into his chest.

His mother's face is all he sees, suddenly, and he hears gunfire again but it's far away, and he's falling.

But he hits the ground, hard, and suddenly there's air.

"Move aside, Captain," a deep voice shouts, and he forces his eyes open and tries to focus. What?

Khan is standing there, hair wild and eyes calm, as deadly calm as the first time Kirk saw him, and he's holding a weapon Kirk doesn't recognise.

He gasps for air, heaving, his shoulder throbbing.

"Move aside," Khan orders again, and Kirk ducks and rolls as fast as he can as Khan opens fire.

He keeps rolling until he connects with something soft, blue material and God, please, no.

"Spock," he wheezes, breath still rattling. "Spock?" He can't see his face. Please.

"I am fine, Captain," comes the familiar voice, ragged but coherent, and Kirk slumps sideways feeling weak and grateful, lets his head rest against Spock's side.

"You're bleeding," he says, feeling warmth under his right hand.

"A superficial wound. You have also sustained an injury."

"Yeah, I'd noticed."

Behind them, Khan is taking down Klingon after Klingon in a dance so assured it looks choreographed, and they stay still, dumbly taking in the déjà vu.

"The others?" Kirk chokes out.

"I am not sure. Doctor Marcus was injured in the first blast. I was attempting to move her to safety when the second hit."

Kirk remembers the siren screams he'd heard and feels sick.

Khan is still working his way through the Klingon forces like it's nothing, and they're starting to thin out, he thinks, he prays. What the hell is Khan doing on the ship?

"I am assuming," comes Spock's voice, as if he had read Kirk's mind, "that Khan has been a stowaway on the Enterprise ever since we left San Francisco."

Logical, Kirk thinks, but only nods. His throat has closed up, thinking of the dead. There will be dead.

Khan pivots on his heel one last time, kicks one Klingon squarely in the face as he hits another with phaser fire over his shoulder, snaps its neck and then finally, there are no more.

Silence.

Except for the whimpers, the low hum of collective pain that is suddenly deafening in Kirk's ears. He can't bring himself to move, his shoulder still on fire.

"What the hell are you doing here?"

"Acting as your bodyguard, it would seem," Khan spits, kicking aside a Klingon corpse and advancing. Kirk raises his phaser instinctively, Spock stiffening beside him.

"Stay right there," he cautions.

"Captain, given what you've just witnessed and your current physical state, do you imagine it's wise to threaten me?"

He feels Spock try to rise, tremble with an involuntary gasp of pain and fall back.

"I'm not going to hurt you," Khan says, a hint of exasperation in his voice.

"Hurt us? You've already killed me once," Kirk explodes, the ludicrous intensity of the situation making his voice high, hysterical.

"Now isn't the time to dwell on the past, Captain. Tend to your fallen family."

And suddenly Spock is moving, saying "Nyota" in a haunted voice and Kirk sees her, pale and broken-looking against a console.

The lights are back on, he realises.

Blood. Blood is everywhere, and the smell of burning skin, and finally the body he's been avoiding is beneath his hands, and it's Chekhov. Half his torso blasted away, his face intact, serene.

Kirk shakes, too hard even to hold himself up, and collapses sideways onto one arm. Closes Chekhov's eyelids with the other hand, stifling a scream. Gathers himself to look around the bridge, properly.

And wishes he hadn't.