*September 15, 2018*

"You're what?" Chloe asked in surprise and stared at Lex. She couldn't believe what she thought she had just heard come out of his mouth. She knew that the man was brilliant, there had never really been any question of that, but now she was starting to wonder if that intellect had come with more than a hint of insanity as well.

"You heard me," Lex insisted. He was sitting at his desk making what looked like detailed notes and drawings. He hadn't turned to look at Chloe since she'd come into the room and demanded to know what he had been doing holed up in that room for the last five days.

"I did," she admitted. "I just didn't think that the sleep depravation had gone to your head quite this much."

"I'm fine, Chloe," Lex said with a sigh and finally turned around to face her. She saw the redness around his eyes and the lines on his face and knew that he was anything but 'fine'. "I really am working on a time machine."

"Lex, there's no such thing," Chloe insisted.

"Yet."

Chloe reached out and placed a hand on Lex's shoulder. "Lex, come one. I need your help. You need to concentrate your efforts on something more worthwhile. I know you miss Clark. God knows I miss him too, but this isn't going to bring him back to you."

"That's not what I'm trying to do," Lex growled. "It *is* possible to change the past and that's what I'm going to do."

"How?"

"You won't understand," Lex said and moved to turn away from Chloe.

She kept her grip tight on his shoulder and didn't let him go. "I'm not stupid. Make me understand," she demanded.

"Fine," Lex said with a sigh. "What do you know about physics?"

"Just the stuff from high school," Chloe admitted.

Lex sighed again. He sounded like he was annoyed that he was going to have to explain more than he had hope would be necessary. Chloe didn't care. This might be Lex's place, but she wasn't going to stand idly by while he consumed valuable resources and produced nothing of value. Organizing the newly formed resistance was a lot of work and she could really use Lex's help.

"Okay, when you shoot a single photon at a barrier with two vertical slits in it, you get an interference pattern on photographic paper when it's placed behind. Do you remember that?" Lex asked.

Chloe nodded. It sounded vaguely familiar. Physics wasn't really something that she had paid a great deal of attention to in school. She had never thought that she would need any of the knowledge ever again.

"Do you remember why?"

"No," Chloe admitted.

"Well one theory, and the one you were probably taught in class, is that the single photon turned into a wave of energy. As that wave hits the barrier, a new wave front emerges from each of the slits and they overlap each other causing the interference that shows up on the photographic paper."

"Okay," Chloe said with a nod. She didn't really understand how a photon could turn into a wave, but she was willing to believe that Lex did.

"Another theory is that the universe actually splits and becomes two separate universes. In this theory, one photon, which is still a particle, goes through the left slit and the other goes through the right slit. Then, since there's no difference between these two universes, they collapse back onto each other, and that's what causes the interference present on the photographic paper."

Chloe nodded again. She understood even less of this theory than of the first one, but again she could only trust that Lex knew what he was talking about.

"So, all of that means that there's an experimental reason to believe that parallel universes may exist," he said.

"But how do you know?" Chloe demanded.

"I don't," Lex admitted, "but Jor-El does, and he says that the second theory is correct. The universe can and does split into separate universes all the time."

"Okay," Chloe said. The strange man had been right on everything else he'd told them, and Lex had seemed to trust his knowledge implicitly. Who was she to question it? "So, I get it. There are parallel universes. How does that lead to time travel?"

"In quantum mechanics, we have something called the uncertainty principle. It states that you can't possibly know both the location and velocity of a particle with complete precision. They have an inverse relationship with each other. If you were to place a single electron within a box and then slowly crush the box to pinpoint the location of the electron, you would find the electron beginning to move with ever greater velocity."

Chloe nodded, still not understanding how any of this related to Lex's obsession with time travel. Her acknowledgement provided him with encouragement to continue.

"If we expand that principle to include the fourth dimension, time, as part of the definition of location, we can theorize that particles may be moving randomly through time. Combine that with the fact that we *know* parallel universes exist, and we get a framework for time travel. If we can make things move infinitely fast, then we can get them to move through time to a known location within a few meters and moments of our target."

"And that's possible?" Chloe asked.

"Yes," Lex assured her. "We're building a machine that will do that right now. That's why I've been down here for days on end. The plans are almost complete."

"But what do you hope to accomplish?"

"I *need* to change the past so that this doesn't happen."

"How?"

"I...," Lex started and then stopped. He looked at her seriously like he was trying to decide whether or not he could trust her. Eventually he nodded to himself. "When I was 22, I had a visit from a future version of Clark. He told me some things, but mostly he convinced me that time travel was possible. It was that conviction that eventually led to everything that has happened afterwards," Lex admitted.

"What?" Chloe asked in surprise.

"It's true," Clark insisted.

"So... so where is this other Clark?"

"He disappeared from the timeline," Lex admitted. "I assume that it's because as he changed the future, his universe ceased to exist and collapsed in on itself."

"But," Chloe protested, "doesn't that mean that if you go back there that you will cease to exist as well?"

"Yes," Lex admitted. "But Jor-El assures me that there's a device we can build to ground me in this timeline and allow me to return to it."

"Oh."

"Do you understand why I need to do this?" Lex asked.

"I... I guess," Chloe admitted. "But it would be really nice if I could get some help from you once in a while. What I'm doing isn't easy either, you know?"

Lex's eyes snapped up and he looked directly at Chloe. He seemed to think for a moment and then he had the grace to look just slightly embarrassed. "I'm sorry," he apologized. "I guess I wasn't thinking about that. I get like this, really focused on one thing. Clark used to have to kick my ass all the time as well." A smile spread across Lex's face as he spoke of Clark.

Chloe smiled back softly in response. Clark would always be a huge part of both of their lives.

"You need me to do something?"

"We have a meeting tonight with Robert and Susan," Chloe informed him. "I'd appreciate it if you were there." Robert and Susan had managed to organize a bunch of people from some of the other small towns in the county. They were interested in joining Chloe's effort to form a resistance. She was confident in her own abilities to organize the effort, but she also knew that Lex's presence would lend credibility to her.

"When?"

"Seven," she supplied.

"I'll be there," Lex promised.

Chloe nodded in response. She still didn't really understand what Lex was doing, although she now believed in his ability to accomplish it. And she had gotten what she had wanted, his promise that he would help her. She just wondered how many more times she would need to kick his ass before both of their projects were completed.

***_***


*September 24, 2019*

"Everything will be fine, Chloe," Lex assured the woman standing in front of him looking so concerned. "We've built the machine exactly as Jor-El specified and all the test materials that we've sent back have made it safely into the past."

"What if you get lost? What if you can't come back?" she asked with nervousness in her voice. Chloe was strong, had proven herself that way over the last year that she'd been living with Lex, but he knew that she was really worried about losing him forever.

"The tethers will prevent that, you know that, Chloe. I'll be gone for four hours and then I'll be snapped back here to this time."

"You have the one for Clark?"

"Yes," Lex assured her and rolled the small device over in his hand. Jor-El had also assured Lex that giving Clark the second tether would stop him from leaving the timeline Lex was going back to and allow the other man to come forward in time to Lex's time line. Lex missed Clark every day and though he knew bringing this other Clark back wasn't going to be like having his own Clark again, he still had to try it.

His plan was to contact the future Clark from his own past and to prevent him from speaking to Lex. Lex was certain that if he never knew about time travel then the events in his own future would never have happened. He would never have become obsessed. He would never have worked so hard to develop space travel and ultimately to try and contact Clark's people.

"And if you don't come back?" Chloe persisted.

"Then you go on without me. We both know that you've been the real leader of the resistance since we started it. I've just been a figurehead, someone that everyone knew, a person they could rally around. It's been your leadership that's allowed us to do what we have so far," Lex told her.

"Lex," Chloe protested.

"It's true."

It *was* true. Lex and Chloe realized early on that they needed to organize some sort of resistance. The world had fallen apart and they were the only ones who had any idea why it had happened. They worked secretly to draw together as many people as possible to fight the aliens who were still occupying their planet. Now their plans were nearing fruition. In only a couple months, Chloe's forces would attack the main alien base and overwhelm it. At the same time, a ship would launch from what used to be LuthorSpace with a specially designed weapon on board that would hopefully destroy the Sengari ship. If it worked, they would at least be liberated for a time. With any luck it would be long enough to build some defenses before the next Sengari ship arrived.

Chloe eventually nodded. "I would miss you."

"I know. That's why I have to come back, for you and for Hope," Lex assured her. An image of the little girl that he now thought of as his daughter flashed through his mind. She wasn't there to see him off. Both he and Chloe had thought it wouldn't be a good thing for her to see. He had said goodbye to her that morning and kissed her on the cheek before leaving her to play with the other children who now lived in the compound.

"Be safe."

"I will," Lex promised.

He stepped back away from the woman who had become like a sister to him over the last year and stepped into the machine. The door slid shut in front of him and Lex suddenly had a strange feeling of claustrophobia. The pod was built for two, himself and the other Clark that he hoped to be bringing back, but it was still confining.

This had to work; he had to change this future in at least one reality. He understood, though, that when he arrived back in his own time, nothing would have changed. That's what the tethers were for. He had considered being selfish and not returning, but he couldn't leave Chloe and Hope here alone if there was a way for him to come back. The most he could hope for was to change some other Lex's future. It would just have to be good enough.

The machine was pre-set. All Lex needed to do was press a button to start the cycle. He reached forward and pressed.

***_***


*August 15, 2002*

Lex knew that future-Clark would be entering the timeline from a location behind the stables, so Lex had purposefully picked a location on the exact opposite side of the grounds. Dave's people would be swarming the stables and would never notice another intruder. That exact incompetence was what had gotten the man fired in the first place, but now Lex was able to use it to his own advantage.

He entered the castle and quickly moved to the hallway that he knew Clark would be in within moments. He needed to intercept the man far enough away from his old office that this past Lex wouldn't hear Clark in the hallway. Lex just knew that he needed to erase this visit from history. This visit from Clark was what had caused Lex to become obsessed with time travel. It was what had caused him to change the course of his own life and eventually build the ship and the transmission device that would attract the Sengari. That couldn't happen. This new future had to be free of any trace of Lex's obsession.

Lex stood at the top of the stairs in the shadows and waited for Clark to arrive. It didn't take long. After only a minute of waiting, future-Clark was mounting the stairs and heading towards past-Lex's office. Lex stepped out of the shadows to intercept the man.

"Clark," he greeted the man. He looked just as Lex remembered and it suddenly hit him that this Clark was older than his own Clark had ever become. He wondered how long he had lived in his own time line.

"Lex?" he asked. He sounded confused and as his eyes roamed over Lex's body his eyes started to narrow. "Who are you?" he demanded. "You're not supposed to be here."

"No, and neither are you, Clark," Lex insisted. "I'm from the future where you went down that hall and spoke to Lex. I'm here to stop you."

"Why?" Clark asked. His eyes flashed dangerously.

"Because it didn't work out. Something terrible happened. If you go in there and tell Lex who you are and where you're from he's going to become obsessed with learning how time travel works. He'll eventually figure it out with the help of your father...."

"My dad?"

"Jor-El," Lex supplied and watched as Clark's eyebrows shot up. "But along the way he'll attract some really nasty attention."

"What do you mean?"

"Where I'm from," Lex started and then shook his head, "No. When I'm from Earth has been invaded and conquered by an alien race."

"My people?"

"No, an old enemy of your people. They... they are not kind, Clark. I don't know how it was when you're from, but it can't be much worse than it is."

"It *is* worse," Clark said softly.

"What?"

"It's worse. It.... You, Lex. You caused a nuclear holocaust. Almost everyone is dead and the people who aren't are sick and dying. There are children born every year that just.... They're not even human anymore, Lex."

"I...," Lex stopped. He didn't even know what to say. How could he have done something like that? "I'm so sorry."

"It wasn't you. I mean you, you. It's just really bad. I need to do something. I need to change it," Clark insisted.

"Okay," Lex conceded, "so we're here to do something. Just not with me. We need to talk to you."

"Okay," Clark agreed after a moment of consideration.

"I need you to take this," Lex said and passed over the second tether that he had brought with him. "You can't lose it."

Clark took the little device and looked at it. "What is it?"

"It's a time tether. It's attached to my timeline," Lex explained. "I have one implanted under my skin here," Lex said and pointed to a spot on his arm. "It will prevent you from disappearing from the timeline. It... it can also allow you to come back to my time if you choose to do that."

Clark looked at him sharply. "Your Clark?"

"Dead," Lex admitted. It was the first time that the words had actually left his mouth. It hurt so much for him to think about his beloved. He had no idea what the Sengari had done to him, but there was no doubt in Lex's mind that the other man was dead.

"How?" Clark asked. There was a slightly accusing tone in his voice.

"It wasn't me, if that's what you mean, Clark," Lex snapped and then sighed. "I'm sorry. It's just... it's hard. I loved him so much. It was the aliens. Over a year ago now."

"So you *were* together?"

"Yes."

"And it didn't help?"

"Well I certainly never contemplated nuclear holocaust," Lex said bitterly. "But no, in the end I guess it didn't really help. The world still came apart."

"Maybe it's fate, then," Clark suggested.

"No. I think we can still fix it. But Clark needs to get through to me before Desiree happens."

"Ok.... Wait. You still married Desiree?"

"Yeah?"

"You didn't listen to me," Clark accused. "I came here to stop you from going to that conference and meeting her, but you still did it."

"I told you," Lex tried to explain, "you fascinated me with time travel. I had to go and see if what you had predicted really came true. Desiree's existence convinced me that you really had been from the future. It convinced me to continue looking for the secrets that I knew you held."

Clark looked like he wanted to call Lex something nasty, but he visibly restrained himself from doing so. He took one step back down the stairs and away from Lex's office. "So, talking to you was a bad idea?"

"Yes."

"What are we going to say to me?"

"Where are you right now?" Lex asked. It was a reasonable question. Lex had no idea where Clark would have been that day. He only knew that he had been in his office receiving a strange visit from this Clark in front of him.

"It's August," Clark reasoned. "I'm probably in the barn moping because I can't find a way to get you to notice me."

"Clark?"

"You didn't think that I just suddenly woke up one day and decided that I liked you, did you? I moped about you for years, I'm sure."

Lex looked over at Clark and found that the other man was smiling. He was making fun of himself and Lex couldn't help but smile back. This man was so much like his Clark. It would be so easy to let them meld together and become one person in his mind, but he knew he couldn't let himself so that. Even if this Clark did decide to return with him, Lex would always need to remind himself that this man was not his mate.

"What happened to me in your timeline? How did I become that evil?" Lex asked as the two of them quietly made their way out of the manor and across the grounds.

They kept as out-of-sight as possible. It wouldn't do to have someone recognize them and wonder what they were doing, especially when they looked so much older than they should have in this time. Clark showed Lex a shortcut through one of the fields that would take them more quickly to the Kent farm.

"I told you that I loved you," Clark started and Lex nodded his encouragement. "We were together for a time, but you always insisted that you couldn't love me back. I wanted you to move in with me and you told me that we were only fucking. I was young. It hurt. I ran away from you and didn't come back. I was never able to love anyone else. You know about that, right?"

"Yes," Lex assured the other man.

"Oh, good. I had no idea what was going on for the longest time. Then Father told me and I was devastated. To be bonded to a man who swore he would never be able to love me back was the worst fate imaginable."

"How did that lead to me trying to end the world?"

"Ah," Clark breathed. "Apparently you, or my Lex, really did love me, but he was so screwed up from what Desiree did to him that he never allowed himself to acknowledge it. Over all those years his love turned into a bitter hate and he eventually decided that he simply couldn't go on living with the pain he was in. He... he wanted me to kill him and he knew that the only way I would do that was if he did something horrific. So, he did."

"You killed him?" Lex demanded.

"I had to. He destroyed the world, Lex. How could I let him go on living after something like that?"

"I understand," Lex said quietly. "I can't even imagine it being like that between us."

Clark nodded but didn't reply. The two of them kept walking. The Kent farm appeared around a bend in the road and Lex knew that they were only another ten minutes away.

"He left me once," Lex said softly.

"What?" Clark asked.

"You.... Clark. He left me once."

"Why?"

"I was obsessed with learning how time travel worked. I was staying in the lab all the time and never coming home. He left, went back to live with his parents for two months over the summer, and told me that he wouldn't be moving back into the penthouse in the fall. I thought I could take it. I thought that it didn't really matter. I was wrong. After only a week I felt like I couldn't function. I held out for another month because I was stubborn and then I started begging him to come home."

"He obviously did," Clark observed.

"He did," Lex agreed. "And we worked out how my research was going to happen. I still spent a lot of time at the lab, but I came home every night. Living without him for those two months nearly broke me, though. I can almost see how your Lex could have done what he did after not being with you for so long."

"I never knew," Clark insisted.

"I know. I can imagine what I said to you to drive you away. I've always been a bastard when I'm scared. We just need to make sure we change the future for this Lex and Clark. None of this can happen again."

They were standing in front of the Kent barn then. It was time to fix the past once and for all.

"No, never again," Clark agreed.