Author's Note:

Leo Luthor was born to prove that Kara and Lena's relationship is deeper than the CW would like to admit. Writing this I've grown fond of Leo, he's my son now, we just created and adopted a fictional character I know how crazy that sounds. I'd like to thank both Mizhuin and belizafryler for their beautiful artwork, be sure to check that out. I'd also like to thank tiiffk for your amazing support and assistance throughout this Big Bang Project. I have enjoyed participating in this, it was so much fun and a great experience! I hope you enjoy my story. Many thanks and much love.

Be sure the check out the beautiful art associated with this story. On AO3, check out my twitter page yep139 for details.

Things always seemed simpler when you tinkered with tech. It was just the project before you, the problem ahead, and every little victory that made things much sweeter. He'd been absorbed in building the portal all morning, well after he had a realization of how to correct the issue. Between Brainy and Leo, they'd been working on building a portal to travel to other Earths. As for why, well why not? A multiverse of infinite possible Earths with different combinations of people, it was a theory that he could see as reality. "Mr. Luthor," The smooth Irish voice of his AI Ida echoed in the lab.

"Yes, Ida?" Leo raised an eyebrow.

"Miss Danvers is waiting in your office. Did you want me to cancel lunch?" The AI suggested.

"What? We were supposed to meet at 12:30…" He began and went toward the desk picking up his watch, his eyes widened. "It's 12:40! Ida, you were supposed to remind me to…"

"I did remind you, and you replied for me to give you a reminder in a few minutes." Ida replied smoothly.

Leo bit his tongue. "Right… I suppose I did." He exited the lab, swiftly walking toward the elevator. He was sure Kara would understand him being late but he was also very hungry. He also missed seeing her this morning for breakfast, there was a fire of course. Supergirl was needed once again so Leo simply headed into Luthor Corp before she returned. Not the most ideal way to begin their mornings but they made due.

As the elevator stopped and he walked out, he saw Jess sitting at her nearby desk outside his office. He smiled giving her a nod before he entered, his green eyes resting on Kara. Her beautiful golden hair pulled back into a ponytail, an orange sweater, a white collared blouse underneath, and a brown and orange striped skirt. She was sitting on the couch and the Chinese food already opened. Leo walked toward her, "Sorry I'm late, I got carried away with my…" He went to lean down to kiss her but paused as Kara turned to look at him, mouth full of potstickers. He laughed softly and pressed a kiss against her cheek before turning to look at the food she brought. When he spotted what was left of the potstickers, he frowned, "Kara! You left me two?"

Kara swallowed and carefully wiped her mouth before raising a finger to object, "I've been very busy today. I had to stop two robberies, I rescued a cat from a tree, and stopped a car crash. So I think I need them a little more than you."

Leo sat down next to Kara on the couch. "Hmmm well, next time we should get a large order of potstickers." He began to plate up his food.

"Ummm well… you see I did get a large order…" Kara said sheepishly.

"I've underestimated your love of potstickers." Leo began to eat his lunch eating the two potstickers Kara left for him but he couldn't blame her too much. His love could eat.

"So how is your project going? The portal." Kara asked since it was all Leo was working on as of late. She remembered bits of the science lingo, but honestly, most of that jargon flew right over her head. Leo's eyes brightened up and Kara knew his inner nerd was going to come pouring out.

"Well, it's going. Brainy is coming in an hour to help me with it. So this portal that I'm building, it can take us to other Earths, other realities. All these Earths exist but we don't encounter them or see them because they vibrate at a different frequency so we don't run into each other." Leo smiled. "So there's an Earth where I'm poor. Or an Earth where you are an evil genius."

"Oh does that mean there's an Earth where you're bald just like Lex? Now that's a frightening thought," Kara teased her one hand slowly taking Leo's free hand.

Leo laughed, "Very frightening."

Kara ran her one hand through Leo's thick black hair, "Yeah… I don't think you can pull that look off very well. Thank god I ended up with the Leo Luthor that's got a full head of hair."

Leo leaned forward, "Good thing I ended up with the strongest and the sexiest Supergirl." His lips slowly slipped onto Kara's as he felt Kara return the kiss. When she had told him that she was Supergirl he was hurt. He had needed time to dwell on this new fact. That his girlfriend was a hero, not just any hero, she was Supergirl. He realized that even though she hid the truth for so long, her feelings for him were still true. She was afraid of how he would react; she was afraid that her enemies would discover her identity and put him at risk. Understanding someone else's viewpoint was the first step and he did give her another chance. Things only grew stronger afterward, and Leo supported Kara as both Kara Danvers and Kara Zor-el.

Leo's lips soon began to travel down her neck and he heard Kara sigh softly, "Leo…" She warned, "Don't start something we can't finish."

"Hmmm…" He muttered against her soft skin. "We got time… the door is closed, Jess is on her lunch now, and we have just enough alone time…" The next thing he heard was the door being pushed over and Leo quickly backed up, falling onto the floor. Standing in the doorway to his office was none other than Brainy.

"I have arrived!" He paused however as he noticed Leo on the floor and Kara her cheeks bright red as he entered the room. He raised an eyebrow. "Have I interrupted something?"

"Yes." Leo hissed.

Kara however shook her head. "Nope!"

Leo stood up then. "Brainy, you're an hour early." The man had the worst timing, Leo had been so close. He just wanted a little alone time with Kara but Brainy pulled the rug right from under him.

"I was eager to arrive because I have an epiphany. We've been going about this all wrong!" Brainy waved his hands in front of him. "My friend, one word! Kryptonite!"

Leo opened his mouth but soon closed it and nodded slowly, "As our power source?"

Brainy grinned, "It's radioactive by nature, even a small rock could power it. We just need to break it down into a non-lethal energy source that won't harm Supergirl."

Leo's smile grew wider and he grabbed Brainy by the arms as he pressed a quick kiss on his cheek. "Ha! You just might be onto something!"

Brainy blinked. "You? Kissed me?"

Leo shrugged, "You're welcome." He turned to Kara then and kissed her. "I'll see you later tonight."

Kara laughed softly at the two before kissing Leo back. "I'll see you for dinner tonight. Don't be late now."

Leo nodded. "I won't. Love you."

"Love you too."

Leo began to walk out of his office with Brainy following behind Leo, "You know Brainy I'm not as upset with you as I was a moment ago." Brainy looked confused, as smart as the man was, he didn't understand women. "You know sometimes couples like to be alone… together."

"Are you referring to when I walked in on you and Kara?"

"Yes…" Leo began and he could tell he didn't get it yet. He cleared his throat. "Sex Brainy."

"Oh, had I know you wanted to be intimate with Kara, I would have avoided coming into your office. I shall make a note for next time." Brainy gave a firm nod. "Don't worry bro. Or perhaps you should text me…"

Leo shook his head. "How about you just come on time, hmm? I don't need to text you about that. Though I Ummm… appreciate it. Why don't we just get back to work."

Using Kryptonite as an energy source was viable since it was radioactive and only deadly to Kryptonians, but still, using the green rock's raw energy to power the portal could be the ticket. They spent hours painstakingly having the Kryptonite placed in the portal to power it. The portal was very large, about 22 feet in diameter, the circular black metal frame housed the wires and tech while the temporary power supply was attached to the back of the ring. The Kryptonite was placed in the power supply. Leo and Brainy set up a temporary level at a safe distance, wires were attached to the lever and the portal. They placed the final touches before they were ready to test, "Right, you ready?" Brainy gave a nod as they stood back behind some protective plexiglass. "On three… one, two, three." He pulled the lever down, the portal gave a whine, sparked, and then sputtered. Leo frowned and turned the lever down and then up again, nothing. He sighed. "Ughh, dammit…" He rubbed the side of his face.

"That was unexpected. I suppose it's back to the drawing board." Brainy frowned as well.

Leo waved his hand, "No, forget it it's late and besides, you have that date with Nia. We'll give it another go tomorrow morning."

"As you wish. I feel that we will find a solution. We are very close, Leo. I'll see you tomorrow morning." Brainy said before he left Leo alone in the lab. Leo rubbed his cheek, "Why won't you work?" He thought to himself as he walked forward, placing his hand against the edge of the machine. Well, there was nothing he could do now. He turned, only for the machine to spark again. He hissed, yanking his hand back before the machine whirled to life. The green glow from the portal bubbling to life. "Shit!" He said as the energy from the portal pulled his body forward and sucked him in.

Leo soon collapsed, his body landing on the hood of a car. He groaned as his hands held his head and all he could see was the night sky above. A few bright stars in the sky but you couldn't see much, not from the city lights that shone brightly over National City. Leo eased himself off the car he had landed on, rubbing his back as he took in his surroundings. Instantly, the layout of the city was off, just slightly. There were buildings he hadn't recognized. His eyes widened, he was in another world. He rubbed the back of his head and as he turned, he saw a homeless man with his eyes wide as he stared at Leo. He had seen Leo drop out of nowhere, and was speechless. The man was short but scruffy, a thick beard, and his clothes were ragged but obviously, Leo needed information. Leo smiled, "Ahhh hi."

"Are you an alien?"

Leo shook his head. "Ummm no, I uhh I'm a scientist. Working on teleporting…" He cleared his throat.

"Like star trek?"

"Yeah, sort of… look I uh need some information you don't happen to know the name Luthor do you?"

He raised an eyebrow, "I might… though that shiny watch might help me remember."

Leo bit his tongue and begrudgingly, he removed his Rolex watch from his wrist and handed it to the man. "Here."

The man grinned and began to place the watch on his wrist. He examined it against his wrist. "That's a really nice watch."

"Yeah, it looks great on you. Now, Luthor." Leo asked again. He needed to get back home and the only way was stealing some tech from the Luthors. He wasn't sure if he could trust anyone in this world or if anyone would believe him.

"Right the Luthors have a huge building downtown National City." The man began to explain.

"Where exactly?"

"It's off Cordova Street." Leo nodded and then walked away from the man. So he just needed to find the Luthor Corp warehouses. Hopefully, their families thought alike, otherwise, this would be a waste. Any tech he could use to find a way back home to his Earth would be worth it well if he could even find a way back home. Brainy would eventually find out that he was missing, but Leo knew finding what Earth he ended up in was like finding a needle in a haystack. This haystack was infinite; the odds of him being rescued were slim. No, he had to find a way home himself.

It took Leo three different locations before one was a success, there were no guards. The only thing that stood in his path was the security system to the vault. If it was anything like the vaults back home then he should easily be able to gain access. The computer should scan for Luthor DNA, which he had, then it'd be smooth sailing. He raised his hand before placing his index finger into the scanner. He felt the machine prick his finger and after a moment, the computer replied. "Access granted." Leo grinned and after removing his hand, he placed his pricked finger in his mouth, slowly walking inside the large vault doors only to find another set of doors. Perhaps this family was more paranoid than his own.

He removed his finger and the computer simply stated. "Please state your name." He didn't reply right away as he considered his options, this Luthor family might have named their son Leo. There was a chance however that he was wrong and that he would fail the second security checkpoint. What choice did he have? He was out of options. "Leo Tiberius Luthor." The computer began blaring an alarm and before Leo could even move, a force field activated, trapping him between the vault and his escape. Well, he had to come to the one Earth that doesn't have a Leo Luthor.

The phone rang, echoing throughout the penthouse apartment and the CEO groaned as she stirred, her arm reaching out and answering the phone next to her bed. "Yes…"

"Miss Luthor, there's been an attempted break-in at one of our warehouses. The thief has been apprehended…"

Lena sighed, "Why are you disturbing me at 3 in the morning if the thief has been caught. Shouldn't you take him to the police?"

"Miss Luthor, he broke through the first security measure. The computer granted him access, it was the secondary door that triggered the security measures and alerted us. We brought him down to L-Corp for questioning and he's been silent ever since."

Lena sat up in bed at the mention that his thief broke in somehow. That was impossible, the only way anyone would be able to gain entry was to break through the vault doors, and even that was difficult enough. Lex had designed those doors to withstand Superman being able to punch his way through. "I'll be there shortly." She hung up the phone before getting up to get dressed.

When she emerged from the room she called Hope, "Hope, I need you to get me the security files on the warehouse on 5th." The AI was there in the penthouse, her head tilting before she went to a computer and retrieved the data for Miss Luthor. She sent the data to her tablet and Lena began reading though the security systems data for the vault. The security footage even showed the analysis of the thief's blood. It wasn't possible, the DNA was Luthor DNA and her mother's.

"Shall I call a car for you Miss Luthor?"

"Yes, Hope." According to this DNA sample, she had a brother, but that was not possible. Even though she was young, she did not remember having a sibling. So what was he, this thief? She was pulled out of her thoughts as Hope spoke again. "Miss Luthor the driver is ready downstairs for you."

Lena gave a firm nod. "Thank you, Hope."

Leo was waiting dressed in black shoes, black pants, and a white buttoned-up shirt. His sleeves rolled up to his elbows, hands cuffed to the metal table. He was in a simple room with nothing but the metal table and two chairs. So logically, his doppelganger will soon arrive and all Leo had to do was convince him that he was from another Earth and possibly gain his help so he'd be home soon. If things went well, normally he would end up in these situations with Kara but alas he was left alone here. His eyes snapped to the door as a woman entered the room. She was breathtaking, her black hair was pulled up neatly in a high ponytail, red lipstick, dressed in a black skirt and red blouse. Her heels clicking with each step as she walked forward to the table before sitting down across from him. This woman's green eyes met his gaze as they tried to read each other.

The way she walked she seemed to command power, respect, and confidence. Leo cracked a smile as realization struck him; he was a woman on this Earth. She was his doppelganger. "Who are you? According to the computer it says you have Luthor DNA and we have the same mother but that's impossible because my mother-"

Leo finished, "Died." Lena froze as he finished her sentence, her eyes hardening slightly. Leo continued. "The computer's not wrong. I'm from another Earth, one where I am the product of Lionel Luthor and a woman who is far too good and too pure to fall for a man like our father. I have an insane older brother named Lex and a stepmother who I can never seem to get any approval from. So, have you heard of the Multiverse theory?"

"You're saying that the Multiverse is real?"

"Of course it's real. There's no other logical explanation, so logically it must be true."

"Suppose I do believe you, why were you trying to break into my warehouse?"

"I needed to borrow some tech so I can build a portal home. I didn't know who to trust here, or if anyone would believe me. I got sucked in and taken here by accident. Brainy and I were working all afternoon…" He sighed. "Anyways I'm stuck here."

Having a doppelganger was the only logical explanation she could consider. The Multiverse theory was just a theory, well that's what she had thought before. Still, the DNA was proof enough that this man was a Luthor, it was infallible proof. He seemed intelligent, intelligent enough to build a portal to another Earth. Maybe… just maybe, she could use his help. Project Non Nocere was in its early stages of development; she knew her goal but how to accomplish it was a whole other matter. "I have a proposition for you. I want to fix people at their core. Rid the world of lies and violence, make people better than themselves. If you assist me, I will get you back to your Earth."

Leo's eyebrow raised, Non Nocere, do no harm. While her goal was just illogical, fairy tales he couldn't help but wonder what on Earth could possess this woman to want to fix people that way. He didn't believe it was possible to change people in that way without mind controlling them. Isn't that how people are supposed to grow, through the hardships? Finding joy in life, friendship, and family? Life wasn't easy, and yes, he could count more times than one where he felt lost. He felt pain and only when he clawed his way through was he able to gain happiness. Life has ups and downs and you have to travel those waves until you make it through. Then the ones standing by you can give you the strength to go on, to fight. People are always going to be imperfect, you just have to find something in them that makes you appreciate them. Take them as they are.

Alas, Leo would assist her, eventually, he might get the reason for her doing this but what choice did he have? "Very well, I guess we're partners." He grinned. "I'm Leo. I didn't catch your name."

"Lena."