In the end, the truth seeker does its job.
After everything that had been sacrificed to prevent it from discovering and subsequently divulging Supergirl's secret identity, it still couldn't be silenced.
Kara doesn't blame the creature and, surprisingly, her secret isn't revealed at the hands of the D.E.O.
No, that would have been too kind in comparison. Too easy, even after all the mind wipes and the lying.
In the end, it's around Lillian Luthor's hand and under Lena's watchful eye that the truth unravels. Reveals itself by way of the matriarch's permanently slyly shaped mouth.
Kara had only been there because Lena had asked her to be. After confessing that she'd gotten her mother released into her custody - by buying the prison - once it had been revealed that Lex had tried to kill her. And again, Lena had confessed with the fear of rejection sparkling like dying stars in her eyes.
And again, Kara had forgiven. Though not because of the hypocrisy she'd be doused in if she didn't, no matter how much truth there is to that. She'd forgiven Lena, for this and for Lex, because she understood how much it hurt to not be able to help your family. Regardless of what they'd done, they were still family. For Lena, there were still good memories attached to Lex and an ever-present need to be loved by a mother who would rather show contempt over compassion.
Forgiving Lena was easy.
Much easier, Kara knew, than gaining Lena's forgiveness for her own secret could ever be.
She'd spotted the truth seeker on Lillian's arm and, noticing her distraction, Lena had explained that Alex had loaned it to her. To ensure her mother didn't try to pull the wool over her eyes again.
And Kara had wanted to leave. Instantly, the need to flee the building began burning inside of her. It was as though every lie she'd ever told Lena had suddenly been set aflame and was revenging her from the inside out.
But they needed to find Lex.
And Lena wanted her help.
So, despite her better judgement and knowing that Lillian knew all about the crest Kara was hiding underneath her shirt, she stayed.
And that was Kara Danvers' final mistake.
But she had hope, as she always did, that if she simply didn't give Lillian a reason to inadvertently out her, she'd be safe.
"I know the answer is here." Lena gestures down at the map she has spread open across the table. Lengths of strings are tacked in place and stretch across the surface of it, marking the places her brother has been. "I know it is."
"My darling daughter," Lillian drawls, sitting atop a workstation and looking more casual than she has any right to. "If you knew, then you wouldn't still be standing here clueless. Lex is out there ready to launch missiles at the United States, and you don't have any idea where he is."
And Lena, frustrated and exhausted, snaps.
"Yes, mother. Tell me something I don't know." She lets her head loll forward and Kara places a comforting hand on her shoulder. It's a touch Lena leans into and then…
"Kara is Supergirl."
Then, everything freezes.
Everything stops and time stands still, and Kara feels the world fall out from under her in a way that's so very different from flying. Ice water runs through her veins and cold dread sweeps along her spine like a frozen wave, its jagged edges sharp and painful.
Lena laughs, practically scoffs, and Kara can practically see a retort forming on her friend's lips as she turns her head to look at her. Something about how Lillian will make up the wildest accusations in order to stall or distract ready to be let loose.
And Kara knows the exact moment Lena remembers what is on her mother's arm because she sees it on her face. Watches as Lena's wry smile falls and fades into a canvas that quickly paints itself in shades of disbelief and betrayal.
"I-" Kara starts without knowing where her sentence will end, her eyes wide and wild.
"Whoops." Lillian lets out a sigh, but there's clearly no remorse in her words. "I guess the cat's out of the bag now."
Lena doesn't look away from her.
Barely blinks.
"Lena, it's- I'm not-"
"She can't lie, Kara." Lena reminds her, shrugging off Kara's hand like it's suddenly burning a hole through her skin. "Something I thought you two would briefly have in common up until about so seconds ago." Her lips tremble as she attempts to smile, but it's mirthless and fails, and drags Kara's heart down with it as it falls.
"No, I didn't mean…" Kara's breath hitches and she realises she's about to cry. "I wanted to tell you. Every single day."
"But you didn't. Instead, you spent every second we spent together lying to me." Lena's voice waivers over 'lying' as if her mouth was never meant to form the word in order to aim it at Kara, and then in a whisper, "You lied to me."
The silence that follows the words is deafening to Kara and she wants to break it somehow, to say something that will fix this. But she doesn't know how.
"You-" a light has gone off behind Lena's eyes. "The kryptonite. Supergirl didn't trust me." Eyes that bore into Kara like daggers. "You didn't trust me. You had James break into my lab-"
"Lena."
"You didn't trust me." It's an echo that's both empty and filled hurt, and she turns away from Kara then, lifting a hand to discreetly wipe at the corner of her eye. Kara's hand shoots out to stop her, lightning quick.
"Let me explain." She holds tight to Lena's wrist even as green eyes glare disapprovingly back at her over a shoulder. "Please, Lena. Please. I never meant for- I didn't want you to find out like this."
"Did you ever want me to find out?" Lena asks and Kara, taken aback by the question, can only stare at her, stunned.
Because the truth is, as much as she wanted to tell Lena, as much as she felt she needed to, there is a part of her that wished she never had to.
With Lena, she could be Kara Danvers. She could hurt and be weak, and Lena would never judge her for it. Lena would hold her and have her back and put herself between Kara and anything that threatened her because she didn't know any better.
Because she felt the need to protect her friend. Her best friend.
With Lena, she didn't have to pretend to be strong all the time.
"You are… unbelievable," Lena practically chokes on the word but manages to spit it out and she twists her wrist out of Kara's grasp. "Get out."
And Kara's so cold now, she's numb. She blinks dumbly at Lena for far too long.
"Please let me-"
"Get out!" Lena's voice is booming and authoritative, almost like her boardroom voice. Only this has a sense of rage to it, of danger and warning, and it's so foreign to Kara. "I trusted you."
Lena doesn't tell her a third time, doesn't need to.
And Kara leaves in a daze.
In a fog created by the debris of a friendship destroyed, one that tries to smother her with every step she takes.
This can't be the end, she tells herself. After everything, this can't be it. Lena can be mad at her, can hate her for as long as she needs, but eventually, she'll let Kara explain.
"She has to," she mutters into Alex's shoulder, the material covering it soaked with tears, later that night. "Right?"
Alex doesn't say a word.
She just tightens her hold on Kara and lets her cry.