Lena sighs deeply as she walks through the network of grey corridors beneath the DEO. She hasn't slept in almost three days. The White Martian attack had been unprecedented and their ferocity in trying to kill J'onn when they realized he was the last Green Martian alive had been brutal.

J'onn is recovering well now and the White Martians have been banished back to their home world once again, with the message that they weren't welcome and their genocidal tendencies would be met with brutal force if they ever tried returning to earth again. The Legends, Superman, Supergirl, The Flash, Star Girl and the other assorted heroes had taken a beating, but they had survived, and they had sent a message to Mars that would likely never be forgotten.

Lena slumps against the elevator as she steps inside. Kara is bruised and bordering on blowing her powers out completely but after a few hours under the sun lamps she should be well enough to come home. Giving into her puppy dog eyes and dastardly pout, Lena has agreed to go home to sleep.

Ideally, Lena would love a hot bubble bath and a few fingers of Scotch but she honestly doesn't have the energy. Falling face first and fully dressed onto her bed seems more likely. Creating the White Martian Neural Defence Wave Generator had been exhausting, even with her old work from Non Nocera to help.

The elevator dings and Lena drags herself out to the underground parking lot which opens to a concealed exit in an alleyway two blocks away from the main DEO building.

Movement from the corner of her eye catches Lena's attention. M'gann is pacing before the Martian ship disguised as a retro powder blue car, her dark cape swinging behind her. M'gann's shoulders are tense, her pace frantic and she seems to be muttering to herself as she rubs a set of keys between her fingers.

Lena hesitates. She is exhausted but M'gann is a sort of friend and after the battle they have all just been through Lena knows she cannot leave the Martian woman in some state of distress.

Lena sighs and drags her weary body across the parking lot, "Hey, M'gann. Shouldn't you be in the med-bay with the rest of the combatants? I am sure J'onn was asking after you."

M'gann startles at Lena's words, but instead of receiving the gentle reassurance that Lena had expected, M'gann frowns and snaps back aggressively, "J'onn will be better off without me. I have no place among the heroes who fought my people today."

Lena halts at the self-loathing that drips from M'gann's words and a stab of familiar pain lances through Lena's heart. Lena knows that sense of self-loathing, she is intimately familiar with how it feels to hate your own people, and see yourself as just another danger to those around you.

"You fought with us today M'gann. You're help was instrumental and you know that J'onn loves you, of course he wants you at his side."

M'gann freezes in her pacing, her dark features a picture of agony as she looks at Lena with such a look of hopelessness and despair.

The keys to the Martian ship clink between M'gann's hands as she drops her gaze to them, "I may have fought with everyone today, but I am not one of them. I am a White Martian. Everyone would be better off if I just left, especially J'onn. How can anyone ever trust me again after they saw the monstrousness of my people?"

Lena's brows furrow, "And I am a Luthor. Where we come from does not define our actions M'gann, and running away isn't the answer. If you think that J'onn would want this, then you are underestimating his love for you to a terrible extent."

M'gann's coal black eyes water visibly and her voice breaks, "J'onn always wants to see the best in me, but I don't know if I can live up to that. Wouldn't it be better if I just ended it now? Showed him how unworthy I am? He would move on. He would be happy, and it would save so much pain."

The words are familiar to Lena, so very familiar. She can't do this here, she can't have this talk in the fucking DEO car park where a thousand hidden listening devices are probably recording their every word.

Lashing out like a viper, Lena snatches the keys from M'gann's hands. The Martian lurches half-heartedly forward but she is so caught by surprise that even with her superior reflexes and strength she is unable to stop Lena's nimble grab.

Lena stuffs the keys into the pocket of her grease and soot covered slacks before spinning on her four-inch heel.

"Come on, follow me," Lena throws absently over her shoulder.

"Hey wait, give those back. I need them!" M'gann cries as she jogs after Lena.

Lena rolls her eyes, "I'll give them back to you once you have heard me out. Until then, the only way you're getting them is if you take them by force. Then again, big bad White Martian that you are, knocking me down to take what you want should be your first instinct."

Lena cuts her eyes to the side and sees M'gann flinch before she rallies, "Give me the keys Lena. Everyone will be better off without me here. J'onn deserves better than being stuck with one of the monsters who destroyed his race."

Lena grits her teeth, "Get over yourself M'gann. J'onn sees you for who you are, not for your race. You might have convinced yourself that you aren't worth his love and your friends care, but you won't ever convince them."

M'gann emits a sub vocal growl that makes the small hairs on the back of Lena's neck stand on end, "You don't get it Lena. Sooner or later I'll hurt him. It's what I am. I might not want to, or even mean to, but I am a White Martian. Destruction is all we are good for. It's all I was for so very long. It's better if I just go, disappear with J'onn's ship. He will feel betrayed, he will be hurt, but it will be the proof he needs that I am like all the rest of my kind. It will save both of us so much more pain in the long run."

Lena steps up to her black Mercedes and pulls out her keys, "Christ M'gann. Hearing you speak is like listening to a recording of myself when I was in my self-pitying twenties and you're what? Six, Seven hundred years old? Grow up and get in the damn car. You're going to hear me out and then I will give you the keys. If you still want to make the colossal mistake of running away like a coward afterwards, well that's your mistake."

M'gann stares at Lena, her eyes cold and hostile even as her tall frame vibrates with emotion.

M'gann's form ripples red and her Martian hero suit reforms into comfy jeans and a leather jacket, "Fine. I will hear you out Lena Luthor but then you will give me the keys, or I will take them by force."

Lena smirks cockily, "First rule of business M'gann: Don't make threats you can't back up."

Without waiting for a response, Lena opens her door and slides her tired frame into the driver's seat.

M'gann stands frozen for a moment in impotent rage before, in a fit of anger, she phases through the car and into the passenger seat.

Lena rolls her eyes again at the dramatics and starts the car.

The two women sit in silence as Lena drives them smoothly through the city towards her apartment. The fires from the invasion smoulder and a hazy smoke sits heavily over National City. The streets remain relatively empty as National Guard and police move like angry ants throughout the city.

They are stopped twice on their journey but a quick flash of DEO consultancy ID badges has the two women breezing onwards.

About a mile from Lena's apartment, M'gann can't stand the silence any longer, "Whatever you have to say, it won't work Lena. I know the Luthor's were hated. Your brother and mother did terrible things but they aren't in the same league as my people. Your family killed a few hundred people, your brother failed to kill Superman and you, you…you haven't killed people. You have done nothing but help the world with your technology and your mind. My people wiped out millions of Green Martians, an entire race, and in the early days I helped. I was one of them. I don't deserve to be called a hero. I don't deserve J'onn."

Lena hums softly, "While I could argue that the issue of scale is irrelevant to whose people were worse and the fact that I have killed an innocent man when testing harun-el, as well as killing Eve Tessmacher and shooting my own brother in cold blood in a previous time line…that isn't actually the conversation I was intending to have with you."

M'gann's arms cross defensively as she studies Lena more carefully, "Lex and Tess were a danger to the world, I am sure that unlike me and my people who killed the pacifist Green Martians, your killings were justified. Also, deaths when doing informed medical testing is sometimes inevitable no matter the safety precautions."

Lena's hands tighten on the leather wheel of her car as she fights back the memories of her past misdeeds, "You give me far too much credit M'gann, but again, that isn't the conversation I was intending to have with you."

M'gann sits in her seat and glares forlornly out at the road ahead.

Silence settles thickly between the women again.

Lena manoeuvres her car into the secure, hidden underground parking level of her apartment building and with quick efficient movements she guides M'gann to the similarly hidden, private elevator to her penthouse. M'gann is quietly impressed at the security as Lena deftly uses a combination of biometric scans, a key card and a twenty-four-digit access code to gain access to her home.

The elevator ride is smooth and quick and before M'gann really has a moment to process she finds herself standing in Lena's glistening marble Kitchen.

"Please, take a seat," Lena says with a negligent wave at the grey sofas in the living area, "Would you like a drink? I have some Martian drel that J'onn left."

M'gann nods hesitantly as she walks slowly to the sitting area.

Mirroring actions which J'onn himself had once done, M'gann takes in the large open plan living space. A large three sided sofa faces a large wall mounted television. A messy mix of animated film DVDs and Rom-coms sit beside an outdated DVD player which is hooked up tpo the TV by a long cheap purple cable. The messiness and outdated technology at odds with the sleek design surrounding it. A scattering of books and magazines lie across one side of the sofa and a soft multicoloured blanket lies in a pile in the middle as though Lena had been disturbed while she was cuddled up on the couch before this invasion debacle started. The blanket is strikingly at odds with the monochrome pallet of the rest of the furniture, but on closer examination M'gann begins to spot other anomalies: A small photo of Kara and Lena in a red wooden frame, a plumeria in a sea blue vase on the marble counter opposite the living space, a painting of what appears to be a red Kryptonian landscape beside the apartment door and at the back of the room, through reinforced French doors leading to a balcony, M'gann can see weather proof bean bag seats in green and blue.

M'gann can feel her lips twitch at the corners as a smile tries to break out on her face. The evidence of Kara softening the Luthor's hard edges since she moved in with her last month are subtle but show Kara's increasing influence on Lena and her life. Slowly, step by step, Kara is invading Lena's monochrome world, one brightly coloured decoration at a time. Turning a living space into a home.

Lena returns to the living area carrying a small glass with thick black liquid which she offers to M'gann even as she sips from her half full tumbler of Scotch.

M'gann raises a brow with a pointed stare at Lena's drink, "Not even a few ice cubes to mix it with?"

Lena snorts, "You sound like Kara. It's been a hell of a day M'gann and to quote my father, 'there's enough water in it without diluting it with ice.'"

M'gann sighs and shuffles to sit on the end on the sofa, "Say your piece Lena and then give me the keys to the ship."

"They keys to J'onn's ship you mean," Lena snarks.

M'gann remains silent but glares at Lena until she sighs and sits on the opposite end of the couch. Lena reaches across the sofa and drags the multi-coloured blanket to herself. She pulls her knees beneath herself and drapes the blanket across her lap. M'gann doesn't miss the subtle sniff of the blanket that Lena tries to hide in her careful rearranging, nor does she miss the way Lena's shoulders subtly relax at the scent memory of Kara.

Lena settles the Scotch between her hands and cradles it like a crystal ball. Lena seems to get lost in the depths of the amber liquid and just before M'gann loses her patience Lena speaks in a monotone. Her voice dead as she drops a verbal bomb between them.

"I cheated on Kara."

M'gann sucks in a breath and she almost topples her glass of drel as she flinches violently at the revelation.

M'gann's eyes are huge as she gazes at the forlorn Luthor. Lena looks broken. Her hair has fallen forward and her shoulders are bowed. For a brief moment, M'gann sees Lena as the embodiment of a painting she once saw with J'onn, 'Weeping Nude by Edvard Munch." While Lena sits fully clothed in her battle rumpled business suit that she has been wearing for three days, she is stripped bare before M'gann emotionally. All the Luthor walls are gone, her defences stripped clean.

Lena raises her head slowly and her face is a rictus of agony. Tears stream slowly from blood shot eyes and the muscles in her face seem pinched as though Lena is being burned from the inside out, her anguish palpable.

M'gann feels righteous anger and questions bubble up like lava. The rage an almost physical force. How could Lena do this to Kara? To sweet, loyal, innocent Kara? By H'ronmeer it would kill Kara!

M'gann's face morphs into one of loathing and rage but before she can utter more that an incoherent, "What?!" Lena is forestalling her tsunami of questions with an open palmed hand in the universal sign to stop as she croaks, "Kara knows. Kara has always known."

M'gann's mind whirls as she tries to grasp this revelation. Are the two women in some oddly human polyamorous relationship or open relationship? The concepts are foreign to Kryptonians and Martians but perhaps Lena pressured Kara into it. Lena could be lying, could be covering herself but surely Lena would know that M'gann would never accept the hollow reassurance of a Luthor's words that Kara knows. M'gann tries desperately to find any hint in her recollection that Lena and Kara have fought, any hint of this infidelity. Kara and Lena's relationship has been ongoing for over two years now, but they have been 'taking things slow' as Kara likes to put it. Their decision to move in together last month had come only after escalating numbers of overnight stays and a trial run of living together for short periods of time.

M'gann had been delighted that Lena was seemingly willing to move at Kara's pace and to allow them both time to acclimate to the necessary compromises and growing pains that two aliens entering a lifetime partnership would entail. Had it all been a lie?

M'gann's voice is cold, "Who? Who could possibly offer anything that would make you cheat on Kara?"

M'gann's mind is aflutter. The human proclivity to adultery and multiple life partners was confusing to her Martian socialisation and biology. Then again, the concept of lies and miscommunications which seems to be part and parcel of humanity has always confused the telepath too.

Would Lena have cheated for business advantage? Sleeping with a competitor, a board member or a fellow CEO for some corporate advantage and bargaining? Ena always joked about using her flirting and femininity to get ahead in business negotiations. Maybe she took it further than flashing cleavage, tight clothes and flirting. Perhaps not all was as well in their physical relationship as their intimate body language, displays of affection and the teasing that made Alex uncomfortable implied. Did Lena cheat for the sexual pleasure that humans often seem addicted to? Kryptonians were never known as the most 'physical' of races but M'gann had always thought Kara and Lena held a great passion for one another. No, perhaps Lena was blackmailed, or it was coerced for Kara's safety and secret identity? There has to be a reason.

Lena shrinks into herself and a fresh wave of tears burst forth even as Lena croakily answers, "She was no-one. Just a random hook-up at a bar one night. Kara was in Gotham helping Kate and I was lonely. I had had a bad day at work and I didn't want to drink alone in my apartment. I don't even remember her name. She was some dumb blond who was happy for me to buy her drinks and listen to me rant about my over privileged board, and then she was happy to eat me out in the bathroom of the bar and let me fuck her against the cubicle door."

The crass language makes M'gann flinch, it makes bile, or the Martian equivalent, roil in her stomach. Lena's profanity paints a sordid and cheap picture.

Lena ducks her head in shame as she sees the disgust curl M'gann's lips.

"So, what? You were lonely, and drunk? What the fuck Luthor? How long has this been going on!" M'gann screams now, her anger bursting forth. She tosses the black drel onto the table. The glass shatters and Lena flinches at the rare show of anger from the usually calm Martian. M'gann begins pacing the room, her hands tugging on her hair as she casts Lena disgusted looks.

Lena drags in a shuddering breath, "It only happened once. It was about six months after Kara and I started dating. Right after Kara was made a formal member of the Justice League and honoured in Washington."

M'gann freezes mid step, "The week Kara and you held up here to 'celebrate.' Kara told us she wanted a 'staycation' at home with you and a digital detox for you both. We all left you guys alone that week thinking you were exploring the physical aspects of your relationship. But really, really you were…"

Lena cuts M'gann off, "…dealing with my infidelity. I confessed to Kara as soon as she returned from Gotham. It was the worst week of my life. I thought Kara would finally see me for what I am. A Luthor. Unworthy. Evil. I thought she would just leave but instead she blamed herself."

"What!" M'gann cries furiously, taking an aggressive step towards Lena. Lena shrinks into the couch and cringes in fear before she can stop herself.

Lena gathers herself and her eyes go distant as she seems to get lost in the memory,

"When I told Kara, she didn't get angry like I expected. Like I wanted. She…she, oh God, she just sort of collapsed into herself and just said 'oh' in this tiny little voice like she expected it all along. I thought it meant she had suspected I wasn't worthy, that I wasn't good enough all along, but then she apologised. To me. The cheating piece of shit that had just defiled herself with some sleazy tramp in a dirty barroom lavatory like a common whore. She apologised to me for not moving fast enough, for not meeting my needs, like it was her fault I had fucking cheated. We had still been taking our intimacy slowly then, weren't at the point of experimenting with sex yet. I was letting Kara set the pace and she blamed herself for me cheating. She tried to hug me, to grasp my hands. I couldn't bear to let her touch me, to have her heroic, innocent hands touch the flesh that had betrayed her, that had been sullied by fucking that bimbo for a brief flicker of the pleasure that merely hugging Kara gives me."

Lena is gasping now and shouting. Her whole frame shakes with sobs and she has retreated to a tight ball in the corner of the sofa.

M'gann gapes at her, "Kara blamed herself. She apologised to you! What sort of evil, manipulative bitch are you? I should fucking tear you apart you…"

M'gann advances slowly but her growled words are cut off by Lena's almost manic, broken laughter, "You think I wanted her to blame herself? I couldn't believe it, I couldn't fathom it. I screamed at her, I shouted my sins in detail to her, every terrible, degrading thing I had allowed to happen in that piss smelling cubicle. I wanted Kara to hate me, I wanted her storm out and be gone, but all she did was just stand there, stand there with those big beautiful blue eyes swimming in tears. That sad look that burned worse than any torture or pain my family could ever have inflicted. I wanted to tear them from their sockets, to dash out those sad blue eyes as they looked at me with love and forgiveness even as I screamed out my shame and my sins. Those eyes were meant to burn with rage, with hate, with the realisation of how unworthy I am."

M'gann freezes in confusion, she can't understand this. It makes no sense. If Lena cheated just for pleasure, then why tell Kara? And if Kara was willing to forgive Lena, or actually take the blame for her infidelity then why didn't the Luthor just let her?

A terrible thought worms into M'gann's mind, "You wanted her to break up with you," M'gann whispers in horrified realisation.

The answer is pulled from Lena, drawn out in agony, "Yesss!" she hisses as she slumps in defeat.

M'gann cocks her head to the side. None of this makes sense, her anger boils anew, "Then why not just break up with her. J'onn said you two had talked out your differences in culture and species so you had some sort of plan to ensure clear communication. Why not just end things? Why cheat you piece of shit? Were you too cowardly to be honest? Too much of a Luthor to lower yourself to be direct and straight forward about not wanting her anymore?"

Lena rears up as though struck. One moment she is curled into the sofa like a beaten dog and the next she is jumping forward, on her feet and angry. Lena marches to stand toe to toe with the furious Martian. Their combined angers almost shimmer in the air as they face off.

Lena gasps for air as she bites off each word with brutality, "Of course I didn't want to break up with her. I fucking love Kara, but I needed her to see what I really am. A Luthor, a cold, broken creature unable to match her, unable to be her equal. I was too selfish to ever break up with her, so I did what I have always done, the wrong thing. I took all my self-hatred and my self-loathing and I ran from Kara's love into the cold arms of some parasite in a bar. I cheated so I could destroy our relationship on my terms, so that it would end before Kara really saw how unworthy I am. I cheated to show Kara who I really am, so she would break up with me because I loved her too much and was too selfish to do it myself. I don't deserve her, and I didn't think I had the right to keep a hero, a fucking Paragon of Hope! I ran from her to prove myself and all my detractors right, just like you want to run away from J'onn."

With these final damning words Lena pulls the keys to the Martian ship from her pocket and tosses them at M'gann.

M'gann has frozen at Lena's words and the keys strike her in her chest before falling to the ground forgotten.

"What?" M'gann croaks, "No, I am nothing like you, I want to leave to protect J'onn, to protect him from…me?"

M'gann trails off and her words die.

Lena shrinks and collapses back on the sofa, "You want to steal his ship, to run away just when he needs you most. You want to prove to him you are a thief, untrustworthy and can't be depended on to be there for him when he needs you most. You want to show him the worst of yourself so you can run away from a love you don't think you deserve, just because you're a White Martian, like I am a Luthor."

M'gann blinks stupidly. The true genesis and reason for this conversation and for her being in Lena's apartment coming back to her. She was about to run. She was thinking she had to hurt J'onn to protect him from her.

"I- I have to protect J'onn," M'gann moans pitifully in a last desperate attempt to justify her actions.

Lena offers her a pained smile, "I thought I had to protect Kara from me too. It turned out that she had to protect me from myself. I didn't count on the fact that she would love me enough to understand my fucked up logic. I didn't understand that she loved me, broken pieces and all. All trying to run from her did was hurt her and make her chase after me. She literally held me prisoner in this apartment for a week talking through my traumas, my self-hatred, my self-destruction and my issues. If Kara wouldn't let me run away, if she wasn't better off without me, then what makes you think J'onn wouldn't be the same?"

M'gann's mouth gapes open and closed as she tries to find a counter argument. She was so sure that leaving was better for everyone.

"Kara forgave you?" M'gann asks hesitantly.

Lena nods slowly, her face filled with wonder, "I still can't believe it. Sometimes I look at her and wonder if I am dreaming but she didn't even forgive me, she just understood. She said there was nothing to forgive, that what I had done was part of our growth, that I had to take a misstep so she could help me understand how much she loves me. How flawed my thinking is. Do I still go down spirals of negative thinking sometimes? Yes. Do I still have crisis of self-esteem and worthiness? Yes. The difference now is that I know I can talk to Kara about it. When Lillian, or Lex, or some twitter troll's voice begins whispering all those destructive thoughts in my head I go to Kara. I talk to her. She banishes them. I don't need to destroy my happiness to save hers. Apparently, my happiness is hers, just as much as her happiness is mine. J'onn is the same, I have no doubt."

M'gann nods slowly, "Kryptonian thinking has always fascinated me. So logical on one hand yet rather than seeing past behaviours as indicative of future ones they assume they act as points of growth to behave in new and different ways. I think, I think I need to talk to J'onn."

Lena reaches tiredly into her bag and pulls out her car keys but when she looks up M'gann has already transformed into her Martian uniform and is striding for her balcony.

Lena mumbles under her breath, "Right, you can fly."

M'gann hesitates at the doors to the balcony, "No-one else knows of what you have told me?"

Lena cannot constrain the pained laugh she lets out, "Do you think I would still be breathing if Alex or J'onn knew what I had done?"

M'gann nods resolutely, offering no reassurances that Kara would have been able to protect Lena from her overprotective sister and space father if they knew of her infidelity, "You would certainly be missing pieces at least."

"No less than I would deserve, "Lena whispers sadly.

"But you have resolved this issue, you would never again make this mistake?" M'gann asks over her shoulder in a level voice.

"Never," Lena husks resolutely.

M'gann nods definitively as though H'ronmeer has spoken, "Then this is an issue between mates and will never again be spoken of. You have my word."

"Thank you," Lena whispers brokenly.

M'gann floats before the balcony doors, "No Lena Luthor, thank you. Thank you for your trust and for preventing me from making perhaps the worst mistake of my long life."

Before Lena can respond M'gann phases through the balcony doors and disappears into the night sky with a whoosh of displaced air.

Lena sags, the emotional and physical tole of the past hours and days striking her like the sky upon Atlas' back. Lena casts a mournful look at the broken glass and spilt drel on her carpet before shaking her head, "Fuck it, I'm going to bed."

Putting words to actions Lena Luthor trudges towards the master bedroom she now shares with her love.

The End.

Notes: This is a one shot. No follow up of any kind. No matter what. I offer the story to all readers as a prompt, go forth and write some good cheating Lena stories or maybe write Lena's side of the events that she is referring to in the story. I don't have the emotional range or time to do it. Thanks for reading and please let me know your thoughts and drop a review.