A/N: This prompt came from AO3 and I hope you enjoy it! Also, if you're coming over from my story 'By Your Side,' I know I haven't updated in a while, but I'm working on it! Thanks for reading, I'd love to hear your thoughts. :)

Her only source of light are moonbeams, and the clatter of battle has given way to eerie silence, and something hurts—burns across her fingertips. Her hands are pressed against Lena Luthor's abdomen and her hands are covered in blood. Thick crimson blood that floods forward and pushes out into Kara's trembling palms and the blood saturates Kara's skin and Lena's clothes. And the dark haired woman's name spills from Kara's lips like the blood from her body.

"Oh Rao, Lena," Kara whispers again. She removes a red-stained hand away to brush a sheen of sweat off Lena's forehead. "You're okay. It's okay," Kara murmurs to drooping eyes as she puts her hand back in place over the hole in Lena's skin.

"Why did you do that? Oh Rao, why, Lena?" Her throat constricts as she talks, whispers that Lena's okay. She'll be fine. She's doing great. Help is on the way.

Kara's gaze is stuck on the CEO—the blood, the pale facial features contorted in pain, and sharp gasps puffing from her lungs, the hand tightening around the blonde's wrist—when it should be skimming the room to confirm that the attackers are still unconscious after Supergirl shoved them across the room and into the floor after Lena dove in front of a Kryptonite bullet meant for Kara.

But they're still passed out and scattered on the office floor and blood is still pouring from Lena's pale skin. "Hey, Lena, I'm going to call Alex, okay? She's gonna be able to help." Kara's voice quivers and tears beg to fall but she bites her lip and swallows the swell of emotions.

"Don't be scared, love, if I…" Lena trails off and pauses. "Just know that it was worth it and these… these past few months together have been the best of my life and some of the only months I've…" she breaks off with a painful gasp, squirming beneath Kara's super strength.

"Just hang on, Lena, hang on. I can't lose you."

"Okay," Lena murmurs, voice breathy and eyes drooping closed to a burning pain in her stomach and the fumbled words Kara whispers to her sister over the phone.

They have to pull her off Lena when they arrive—all the DEO agents and medics. Kara's grip is so tight, that no amount of prying removes it and instead Alex is at her sister's side and it takes a complete minute of soft words for Kara to inch back enough for the medics to take Lena.

Kara stands slowly as Lena disappears around the corner in a flood of tactical gear and a stretcher. Alex steps closer to Kara and the blonde stumbles slightly into Alex's arms. Her fingers brush the agent's shirt and Kara lets out a sharp yelp. "What's wrong?" the brunette asks, leaning back to examine Kara. "Oh, Kara," she gasps softly. "Your hands." She wraps her palms around the younger woman swaying unsteadily with each moment.

" 's a kryptonite bullet," Kara mutters and still, she won't make eye contact with her sister. "It was meant for me. Lena's in pain because of me."

"No, Kara, that's not true," Alex says, voice warm as she tugs Kara closer.

But Kara shakes her head against Alex's shoulder. "Yes it is. It is, Alex." And her breath is shaky, her mind running a continual loop of Lena jumping in front of Kara and crumbling to the ground as deep red blossomed across the white fabric of her shirt. "This is my fault."

/

Lena's in surgery and Kara's stuck waiting. She closes her eyes and buries her head in her arms all pressed tight against her knees with her hands pushed against her ears. She focuses on the numbness boring through her chest in an attempt to block her senses from the surgery and the clatter of metal and she searches for Lena's heartbeat amongst the hum of the city and the DEO and every other human in the world. It's hard to find even though it's right in front of her.

She feels a gentle touch on her back and uncurls herself just enough to look up when she hears her sister say her name.

"Alex?" Kara asks softly as she blinks blearily, they'd been separated when Kara arrived at the DEO and Supergirl was sent for a medical check despite her protests while Alex interrogated the new additions to the DEO's prison cells.

"Hey," she says and steps forward to take one of Kara's hands into her own.

The blonde catches sight of Maggie beside Alex and straightens. "Maggie," she hiccups and feels words escaping her. It's so hard to talk with the chaos in her head.

"Hey, Kid," Maggie says, rubbing Kara's shoulder with her thumb. "You okay?" she asks just as Kara runs her free palm along her Supergirl skirt and her fingertips collide with sticky drying blood. Lena's blood.

Before Kara can respond, a sob bursts from her lips and suddenly her chest is heaving and her lungs gasp for breath in between the shudders that wrack her frame in the cold, plastic waiting room chair. Hot tears spring from her eyes and scorch her cheeks before splattering against the tile floor.

"Okay, it's okay," Alex says softly as she reaches out to tuck a strand of hair behind Kara's ear and brushes her wet cheek. At the contact, Kara lurches forward into Alex's arms and buries her face into her sister's shoulder, as tears and hot breath touch her skin. "Kara, she should be fine. I talked to the doctors on the way in and Lena's already out of surgery. She'll be awake soon."

The words only push another strangled sob from deep in Kara's chest and she grasps Alex tighter. Everything had been so terrifying—a jolt to her system as the startling realization descended upon Kara that she couldn't keep Lena safe, that she put Lena in danger. Alex holds Kara with one hand and runs the other through her blonde hair over and over again.

Maggie rubs circles across Kara's back and the blonde lets one hand slip from her hold on Alex to take the detective's open palm. Maggie curls her fingers around Kara's and the blonde grips back, her hurricane of sobs ebbing into small hiccups and sniffles until she leans away from Alex and Maggie, drags the back of her hand across her cheeks, wiping away silent tears still streaming across her skin.

A hole is burning in her heart and pain is radiating through each cell of her body and it's the kind of ache that no powers or solar lamps or medicine can take away. There will be no relief, no cure. But she can protect Lena, even if she can't protect herself. She will keep Lena safe even if it makes her feel hollow and jaded and hopeless.

Kara untangles herself from the two women in front of her and with one last quivering breath she pulls herself back together, lets a blank expression fall across her face. When she speaks her voice is empty. "I know what I need to do." Then she turns around and leaves, closes the distance to Lena's room.

/

It takes Kara two hours to gather the courage to do it. Two hours to confirm that Lena's okay and stable and that nothing permanent has occurred, except for a bit of scar tissue that will one day form. Two last hours to soak Lena in, to observe from afar the softness of her hands and hair and lips. The only contact she allows herself is a gentle grip around Lena's fingers. Kara doesn't worry about memorizing Lena's heartbeat or the sound of her breathing—she can listen to that even when they're apart and she keeps her distance. She will grant herself that small mercy.

She feels a little like she's drowning as she chokes out the words before she disappears. "I love you, and that's why I have to leave you."

The fabric of a red cape is swallowed by the night.

Lena cracks her eyes open.