Sarah and Cosima share Felix's bed while Felix sleeps on the couch with Kira. Once, Sarah offered to let Cosima have the whole bed - after all, it was important for her to sleep well. She was silently relieved when Cosima protested. Neither sister can imagine spending the night alone.

Sleep is generally hard to come by for Sarah. She lies next to Cosima under the blankets, her eyes closed, and tries to ignore her ever-present worry long enough to fall asleep. She cries in her sleep to dreams of checking Cosima's pulse, only to find her unbreathing; jolts awake to dreams of Kira, passed out on a hospital bed, giving more and more bone marrow until her heart, too, stops beating; and she often wakes to the very real sound of Cosima coughing, blood splattering the bedspread or the floor or the bathroom sink. In just the last few days, the bags under her eyes have grown dark and heavy.

There are moments of peace, too. When Sarah and Cosima's fingers wind together under the sheets, a reminder that neither is alone. The way they whisper late into the night, and Cosima tells Sarah about the stars and galaxies, and tries to make her understand the vastness and the beauty of the patterns repeating throughout the cosmos, and Sarah can't help but think that it's more like magic than science.

One morning, Sarah wakes to Kira standing beside the bed, holding a cup of coffee. She says, "Uncle Felix made it for you," and Sarah replies, "Aw, thank you, monkey," and Kira hands her the cup and climbs up to sit on the bed between her mother and her aunt. Cosima is still asleep, turned on her side towards Sarah. The pillowcase has a new stain, right at the corner of Cosima's mouth, where blood has seeped out between her lips during the night.

"Aunty Cosima." Kira shakes her. Sarah feels her breath catch as Cosima does not respond, and then a wave of relief as her eyes open slowly and her lips turn up in a small smile.

"Heya, Kira." Cosima sits up, and Kira nestles into her arm, holding out a story book. Cosima smiles and takes it from her. Her hands shake as she opens it, but she manages. She clears her throat and begins to read.

Sarah checks her phone, knowing what she'll see. A text from Delphine, the same every morning: How is Cosima? Sarah types out: Everything's alright. As she presses 'send,' she almost believes it.

An hour later, Kira is out with Cal, who has been promising for days to take her to the bookstore. She wants to buy new stories so that Aunty Cosima doesn't get bored sitting at home all day.

For once, Felix has found it in himself to do some decent grocery shopping. Now he stands in the kitchen, faced with the challenge of storing such products as canned beans and peanut butter when most of his cabinet space has already been dedicated to excess painting supplies and booze. He bounces between the fridge, the few remaining unused cabinets, and the bags on the counter while Sarah paces back and forth in the other room, talking into her phone.

"Yeah, Delphine, she's fine. She's napping," Sarah sounds tired; no doubt, she's answered the same question at least five times over the course of the conversation. But she can't blame Delphine for being on edge. "Call if you make any revolutionary breakthroughs, okay?" She hangs up and stops pacing, turning to Felix.

"Delphine's still working on it. On the cure, I mean." Sarah repeats the information more for her own benefit than Felix's. Delphine has kept in touch with them as much as possible, even found herself an undercover lab in Frankfurt where she continues her investigation of Cosima's genome. "But she didn't sound…" Sarah sighs, "...optimistic."

"If anyone can figure it out," Felix says, shoving a frozen pizza into the ice chest, "it'll be Delphine."

"Yeah, I know." Sarah sits down in one of the living room chairs and puts her feet up on the coffee table.

"Now, if you want to know what I think," Felix's says, walking over to her, waving a dirty dishcloth, "you need to get some fresh air. Stop worrying for just a little while, Sarah."

Sarah opens her mouth to protest, but stops when she sees Cosima standing at the top of the stairs leading to Felix's bedroom. She holds her oxygen tank behind her and braces her other hand on the doorframe.

"Morning, Cos," Sarah says, a little too cheerily.

"Morning." Cosima's voice has become progressively more raspy over the past few days, and today it's not much more than a broken whisper. Sarah remembers the coughing fit the night before; it lasted several minutes and left the bathroom mirror, sink, and floor splattered with blood. Cosima tried to wipe it off herself, but Sarah dragged her back to bed and then returned to do the clean-up on her own.

"Sort-of morning," Felix says, "It's almost noon."

Cosima moves to take the first step down from the bedroom, but her knees buckle beneath her and she hits the ground, banging her arm on her oxygen tank as she grabs at the doorframe with her other hand. She slides down the two steps and lands on the carpet in the living room. Sarah jumps up and bolts to her side, reaching for her.

"Cosima!"

"No, it's okay. I'm fine. Just… tripped, kind of." She takes Sarah's hands and holds them as she catches her breath. Felix, too, is by her side now, standing up her oxygen tank. After a moment, Cosima puts one arm over Sarah's shoulders and tries to stand again, leaning on her for support. Her whole body shakes like she might collapse again at any moment.

"Easy now, Cos."

"I'm okay- thanks." But halfway up, she starts to cough. She doubles over, taking Sarah by surprise, as she tries futilely to catch her breath. She coughs again and again, blood coating her lips and spattering the ground, dripping onto her own clothes and Sarah's.

"Whoa, okay, come on." Sarah lowers Cosima back to the ground, where she braces herself on the floor with her arms. The coughing continues, racking Cosima's body. Sarah holds her, rubs her back, waits for it to be over. Felix runs to the kitchen and wets a cloth, returns and hands it to Sarah. She wipes Cosima's forehead, which is beaded with sweat as she gasps for air between coughs.

"It's gonna be okay. You're gonna be okay," Sarah murmurs, although she's not sure if Cosima can hear her. "Hang in there, Cos." Panicked tears wet her eyes, but she doesn't let go of Cosima to wipe them away. Several minutes go by; Cosima coughs and sputters; Sarah holds her, probably too tightly, but that doesn't matter right now, because she can't let go.

Finally, the coughing stops. Sarah lets out the breath she's been holding, while Cosima takes in shallow, ragged gulps of air. Sarah re-adjusts the cannula, which has slipped out of Cosima's nose. She strokes Cosima's cheek, wipes a bit of blood from the corner of her mouth.

"Okay...okay," Sarah says, getting hold of herself again, "It's over, it's okay."

But it's not over. In one abrupt movement, Cosima's arms give out and her head hits the floor while her entire body convulses again. Sarah cries out in surprise. The cannula jerks back and forth with the convulsions, sliding in and out of Cosima's nose. Cosima claws desperately at the carpet, at Sarah; she can't breathe.

"Felix, help!" Sarah's scream borders on hysteria, and Felix bolts to the table to grab his cell phone. "What are you doing?!" Sarah screams again, "Help me!"

"I'm calling an ambulance, you twat!" Felix yells back, dialing and holding the phone up to his ear, his hand shaking.

Sarah rolls Cosima from her stomach onto her back, then grabs one of Cosima's hands with both of her own. She squeezes, and Cosima squeezes back, full-force, too hard, fingernails digging into Sarah's skin.

"Cosima! Cosima, please. Please hold on, Cos," Sarah knows her words won't do any good. She can only stare down at Cosima's pale face, watching the muscle spasms contorting her body this way and that as she chokes on nothing.

Sarah cries in earnest now; tears splash onto Cosima's shirt below her. She's screaming, just noises, incoherent, frantic and despairing. She grasps Cosima tighter, pulls her head into her lap, holds her closer. Cosima looks up at Sarah, her eyes bulging, her head jerking side to side as she fights for breath. Her chest is quivering, her lungs unable to expand. Their hands grasp each other even more tightly.

"Don't leave me, Cosima, please!" Sarah sobs, "Please." She drops her head so she's looking directly into Cosima's eyes. Sarah's hair falls around them like a veil, so they can see only each other, and they gaze into each others' reddened and tear-filled eyes. Cosima has stopped writhing now, like the fight has leaked right out of her skin. She looks up at Sarah, her face twisted in anguish, her mouth open.

Cosima wheezes, an almost squeaking noise which doesn't sound quite human. She makes eye-contact with Sarah, stares directly at her for a moment, and her eyes roll back in her head. Her body jerks, then twitches, then shudders, and then she stops moving altogether. Her hand goes limp in Sarah's, and their arms fall together onto her chest.

"Cosima," Sarah says, lifting her head so she can see the whole of her sister's still body. "Cosima!" She squeezes Cosima's unresponsive hand, squeezes so tightly she could have broken it. And then she drops it. It lands back on Cosima's chest with a soft thud, and then slips onto the ground beside her. Sarah grabs Cosima's shoulders, still in her lap, and shakes her - violently, desperately, sobbing.

"Cosima!" Sarah grasps her shoulders harder, pushing and pulling with all her strength, as if enough shaking might wake her sister up. But Cosima remains flaccid and ghostly white. Sarah chokes on a sob, turns it into a cry of pain, and thrusts Cosima's head out of her lap. It hits the floor with a thunk. Sarah is on her feet, bounding across the room, banging her fist into the wall; banging her head into it over and over and over. She's tearing into the kitchen, yanking open cabinets, snatching out bottles of soda and beer and paint, slinging them onto the ground where they smash and liquid splashes up onto the cabinets and walls. She's in the bedroom, tearing blankets and sheets off the bed, stumbling into a lamp which falls to the ground and shatters. She's knocking over paintings, kicking over chairs, ripping books off shelves. She grabs Cosima's laptop from the bedside table and throws it to the floor.

"Sarah- Sarah!" Felix is by her side, reaching for her wrist. She yanks it away. She turns to him, opens her mouth like she's going to say something, but then screams instead. High-pitched and bestial, her hands fly to her head, pulling at her hair; she looks feral.

Hesitantly, Felix moves to touch her. "Sarah," he says, as she whimpers and tugs at her hair and chews on her bottom lip so hard it begins to bleed, "I called an ambulance." He must know that an ambulance is no use now. He must know that. Sarah turns away from him and rams her head into the wall once more.

"Sarah- don't!" He grabs her by the shoulder, but she shakes him off. She races across the room and flings herself down next to Cosima. She grabs Cosima's hand with one of her own, wraps her other arm around her, pulls her close. She presses her lips to Cosima's cheek, tastes salt water and snot and sweat and blood, and she doesn't know if it's her own or her sister's, but it's the same anyway, it doesn't matter.

She heaves air in and out through her mouth until her breath begins to steady. She can hear the sound of sirens through the window, still a few blocks away, much, much too late. She presses Cosima's head to her own chest, pulls her closer so that their whole bodies are pressed together.

"You said you wouldn't leave me, Cosima," she chokes, "You said you wouldn't." And it doesn't matter that Cosima said no such thing, because this was the kind of promise that resonates somewhere beyond words, and Cosima has broken it. And so Sarah lies there with her, hands clasped, tears still falling behind closed eyelids, listening to the sirens, and hearing Cosima's voice whispering "You're a survivor."