A/N: Here's the last chapter! As always, thanks for sticking with me. :)
"I need to take her," Alex says to the doctors. "There's no time, I know my sister's physiology. This is our only chance."
Dr. Hamilton steps back, motions for the others to do the same. "What can we do? You make the calls, Agent Danvers."
Alex nods gratefully. "Help me get Kara on a stretcher, we need to get her to the basement."
She's moved, sweating through the sheets and mumbling in Kryptonese—words that Alex knows don't go together, words that are sharp and pained between strangled breaths.
"The Kryptonian DNA in the sample wasn't a mistake," Alex says as they roll Kara's stretcher down the hall. "The cell is mutated to mimic Kryptonian bacteria, that's why it didn't match any of samples I had… that's why the kryptonite made Kara better at first; it was killing the bacteria."
"So we give her more kryptonite?" Lena asks, calling from behind the stretcher. "Why do we have to move her?"
Alex shakes her head as they squeeze into the elevator. "She can't handle anymore, her body is too weak. But the bacteria… autotrophic and mimicking Kryptonian cells? It needs sunlight to survive, the bacteria's been taking it from Kara's cells, making her weak and simultaneously triggering an immune response with the infection."
"So no sunlight, no bacteria? It'll die?" Maggie asks, yelling over the clang of the stretcher against metal as they shift it out of the elevator and into an underground corridor.
"In theory, yes. And their life cycle is short, so hopefully depriving them of sunlight for a few hours will be good enough and then all Kara's body has to do is fight off what's left of the infection and its symptoms," Alex says, pausing outside the door to an empty storage room. "Listen, what she's about to do might be dangerous. I want you guys to wait outside, so you don't get hurt by accident."
Dr. Hamilton nods, pulls her team aside and tells Alex to call out if they're needed, but Lena and Maggie push on, follow into the room.
"I'm staying," Lena says.
"Me too," Maggie adds before Alex can protest.
She's about to say something anyway when Kara lets out a sharp cry, tightening the arm around her stomach as her lungs wheeze. "Come on," Alex says, tilting her head further into the room and closing the door behind them.
"But leave the lights off, I don't want to risk even the smallest amount of UV rays for these first few hours, we'll just use a flashlight. Stay to the side," she says before turning back to Kara. "Hey, Kara, I know you can hear me, okay? I need you to listen, can you do that?"
Kara twists, murmurs in Kryptonese and Alex replies back in foreign tongue before switching to English. "No, no, no Kara, you need to solar flare."
"Can't," she mumbles weakly and Lena can barely make out the words. "No strength."
"The bacteria are using the light absorbed by your cells to make themselves stronger, to reproduce, while they take away your powers and make you weaker. The infection is only going to get worse, Kar, you need to do this now."
"Alex," she whimpers.
"I know." Alex sinks in front of her sister, kneeling and taking Kara's hand in her own. With the other she brushes back blonde hair and Kara closes her eyes, tears leaking out of the corners. "I know you're miserable and I know everything hurts and trust me if I could do this instead of you, I would, but I can't, Kara. It has to be you."
There's a knock on the door and J'onn appears. "Dr. Hamilton told me your plan, this will help." He raises a small black box towards her. "It can absorb her heat vision, minimize the destruction."
"Thank you," Alex says and he nods.
"Thank you for keeping your head in this, Alex. You've done well. We'll get a room set up with lightning that doesn't give off any UV rays, I have agents on it now," he says and turns to Kara. "It's time to finish the job, Supergirl. We all know you can do it."
He squeezes Kara's hand and closes the door behind him.
"All right, Kar, just focus and go as fast as you can."
Alex hands Kara the small box and seeks out Maggie's face in the darkness. She catches her gaze, illuminated by only dim light pooling in from the bottom of the door, sends a smile Alex's way and nods.
Alex gives a shaky smiles back and turns to Kara, helping her sit up. "On the count of three, ready?"
Kara pulls in a quivering breath. "Ready."
"All right, one… two… three…"
It's slow at first—heat vision that sparks and flickers, with progress that crawls as Kara whimpers against the pain.
Lena bites her lip, twists her fingers together.
Maggie grabs her shoulder. "It's okay, she'll be fine."
"Come on, Kara," Alex whispers. "Come on."
The blonde's grip around the rails of the stretcher dents the metal.
A stream of solar energy bursts forward; an unrelenting torrent to Kara's cries.
The blue beams shift to white. The box shakes in front of her.
Kara's wail turns sharper, morphs into a scream that makes Alex's heart clench; and then, nothing.
Then, silence for a beat of her heart before the box falls, clatters against the ground and Kara slumps backward.
Then, Alex rushes forward catches Kara's head before it can slam against the stretcher, gently lowers it instead. "No powers, right?"
Kara shakes her head. "Nothing."
"Good job, Kara," Alex says, can't help but pull her sister back up and into a hug, holding Kara so they're pressed together and her worried tears finally fall, drip into blonde hair. "You did so well. The bacteria are going to die soon without the light in your cells to use, we'll run a test in a few hours to make sure it's safe. You might feel a little worse before you get better, now that you've solar flared, but pretty soon it will all be uphill. We'll give you a few days of recovery without sunlamps and hang out here for a bit, but it's okay, you're going to be okay."
Kara nods, curls a sleepy fist around Alex's hair. "Stay?" she asks and nothing in Alex's world could ever make her say no.
"Sure," she says, shifts to move them but Kara's already asleep in her arms, her last view the softly lit faces of Maggie and Lena behind Alex, smiling gently.
"I'll go grab you two some blankets and pillows and see if we can get an actual bed from the med wing in here," Maggie says. As she leans over she sees the tears on Alex's cheeks, presses gentle kisses against them. "She's okay, Alex, you did it." Maggie tilts back, smiles at Lena. "You guys both did."
Alex nods, wiping her cheek with a hand over Kara's back. "Thanks, Maggie. I'll see you in a sec," Alex says and Maggie nods, kisses her head one more time and ruffles Kara's hair before disappearing.
Lena lingers a moment longer, hovering near the edge of the stretcher. She reaches out a hand, wavering for a second before running her fingers over Kara's hair. Lena looks toward Alex, smiling when the older woman gives her a nod.
"You did well, too, Luthor. We couldn't have done this without you."
Lena swallows and her voice is thick with emotion, a quivering whisper in the dimly lit room. "I care about her."
The look Alex gives her is gentle and warm. "I know. She cares about you, too."
Lena looks like she's about to say something when the door to the room bursts open and Maggie waves around some blankets, pillows tucked beneath her arms. They set them up on the bed that Dr. Hamilton wheels in behind her, help move Kara. And Alex keeps the blonde close, never lets the grip on her sister break, not as the medical staff flit in and out, begin necessary tests; not when J'onn comes in to check up on things or Eliza calls
They wait, for time to heal Kara, for the tests to come back.
They wait, and Alex holds her sister close.