"You usually do me the courtesy of knocking, Supergirl," the youngest Luthor stares glassy-eyed, over the rim of her tumbler.

"You usually have a door."

Lena shrugs noncommittally as the Girl of Steel picks over the carpet, strewn with chunks of concrete and exposed rebar. She nudges what looks like an arm, small and cracked, though intact up to the shoulder, no doubt the remnants of some statue shattered in pieces somewhere. The image sends a shiver up her spine as she toes it gently with her boot before crossing to stand before the woman of the hour.

"Shouldn't you be celebrating? You've managed to save this city, this planet. Again." Kara touches her fists to her hips, hoping the stalwart pose will drum up the courage and confidence she is lacking at the moment. Lena deserves a proper thank you, her own sadness, her own loss, can wait. "We're grateful."

"Why?" Kara almost staggers back at the chill in Lena's voice. She watches as the woman tips the contents of the glass back, draining it in one burning gulp.

"Why? You saved everyone. You – you – defeated Rhea, you made it impossible for the Daxamites to conquer the Earth, to ever even think of coming back." The blonde turns, her cape swinging slightly with the abrupt motion, and she crosses to the steel box, wired and whirring, still. "You took something terrible, something created for the sole purpose of killing me and my cousin, something born of hatred, and you used it to save the entire planet, Lena."

The Luthor leans forward, picks up the carafe and pours another two fingers of whiskey into the waiting highball. Kara crosses and gently lifts the glass from Lena's lithe fingers, setting it on the crowded desk before the woman can protest.

"Tell me, Supergirl," the words have an unfamiliar bite and Kara almost flinches at their sting, "had it not been for me – had I not been so eager to trust Rhea, so hungry for her validation and support – would any of this have happened in the first place? I built the portal, I brought them here, I trusted the wrong person."

"And you saved us all."

"But at what cost?" Lena's voice rings high, forced through a filter of anger and guilt. "People died at Daxamite hands. By allowing her to help, my mother might have earned back the city's trust, which has the potential to be far more dangerous than any of us realize," the words are spilling, wet and toxic from the Luthor's mouth, "and I have most likely ruined one of the most important relationships in my life to set things right. If Kara never speaks to me again, I wouldn't blame her."

"Lena," in a flash of crimson and blue, Kara is sitting beside the Luthor heir, lightly holding her shoulder while the woman wrings herself out. "If anyone understands everything you've been through over the last few days, it's Kara Danvers. How could you ever think she would be anything but proud?"

"Proud? Of what? I've ruined her relationship with Mike, Mon-El, that Daxamite boy." Lena turns slightly into the Kryptonian, tangling her fingers in the loose edges of Kara's cape. "He can't survive here now and he can't ever come back."

"She'll understand, Lena." Kara's heart is breaking, over and over, breaking for the love she's lost to the stars and the one fighting so desperately against her own nature, condemning herself to solitude and guilt. The blonde, fighting back her own pain, sacrificing it for the greater good, shifts, drawing face to face with the Luthor heiress. "She knows you would never purposefully cause her pain, and she wouldn't want you to blame yourself like this. Put your blame where it belongs: Rhea.

"She took advantage of you, of your drive, your brilliance, and your good heart. I know you, Lena Luthor; you saw only the potential for good in what she presented She gave you validation, yes, but you wanted to build that portal as a gift to humanity and Rhea corrupted that gift. She is responsible for its misuse, not you."

Kara drags a slow thumb across the apple of Lena's cheek, taking tears with it. The blonde allows her arm to settle around the Luthor's shoulder and the Lena catches her wrist, pulling her closer. It feels intimate, familiar somehow, the two of them pressed together against a backdrop of loss and latent guilt, settling into one another.

"But Kara won't, I mean... I'm the one who flooded the atmosphere with lead."

"You managed to repurpose the diffusion device – which was absolutely brilliant, by the way," the Kryptonian pulls back the curtain of Lena's hair and tucks it behind one ear as she speaks, "but never forget, Lena, I was the one who pressed the button. I made that choice. I knew exactly what would happen, what it would mean to Kara, to trigger the device and I made the decision. You created something amazing and then trusted me with the choice to use it or not, I will never forget that. And Kara Danvers will forgive that."

"I hope so," Lena settles her head against the sway of the Kryptonian's shoulder, still weaving the cape through her fingers. "I'm not sure I could survive another loss."

"You won't lose her, Lena. Trust me." Sirens ring in the distance and Kara shifts slightly. "She didn't send me up to that spaceship in the middle of a war on a whim. She loves you. Trust her to stay. She did promise, after all."

The siren grows louder now, close enough that Lena has picked up it's panicked cry.

"You can't, though, other people need you far more than I do, of course." The Luthor draws back pushing any lingering tears from her cheeks with hasty palms as Kara rises from the couch, "Supergirl? If you see Kara, tell her... tell her I'm sorry."

"She knows, Lena." Kara crosses to the blown out windows leading to the balcony and pauses a moment. "She knows. And she's not going anywhere."

And with that, Supergirl launches from the littered balcony, cape snapping in the updraft. She's almost a mile away when the sound of Lena's heartbeat finally starts to fade from her ears and she can't be sure, but she swears she hears the ghost of an echo leaving the Luthor's lips as she soars.

"Thank you, Kara."