A/N: Alright, so this is based on the Doctor Who episode "The Girl Who Waited," but it's not necessary to have watched it to understand the fic. Tell me what you think! Enjoy!

Arthur was dying. It was such a simple thought, but it took Merlin's breath away. Arthur couldn't die. There was so much he'd never told him, so much they'd never done. Merlin had always sort of had the impression that you died only after everything you were meant to complete in this life was done. But that most certainly was not true for Arthur. It was like Merlin could see the king's life force slipping out of him with each exhale, his soul growing dimmer with each blink.

Merlin was accustomed to death. He had seen many people die—friends, family, enemies. Some at his own hand. He had even seen Arthur on the brink of death, but he had always come away the victor. And Merlin supposed that all the narrow escapes and last minute cures—though he had always been terrified of Arthur's death—had made it feel as though Arthur had some level of invincibility. But he was now realizing that someone could be ripped away from the world too soon. There were some destinies that were never fulfilled. The comprehension made his head spin.

But there was still time. As long as Arthur's heart beat, there was still time. And he was Emrys. Time was all he needed.

Time… The word brought back the memories of being trapped in the Crystal Cave. While his father had spoken to him and showed him how to use the crystals, Merlin had come to the understanding that time was not as linear as he had imagined. It could be manipulated and changed, bending and twisting and turning like a snake in the grass or water around a rock. He could slow time, see the past, the future. And as he had walked into the blinding light in the cave, he knew he could do more than that as well. He could rewind the years, or skip to later ones, or be in two places at once. But he also knew there were some things that could not be changed. And Mordred plunging his dragon flame sword into Arthur's stomach was one of them.

There has to be something, Merlin thought desperately. Some way to heal him without the help of the Sidhe. Avalon was simply too far away for Arthur to reach in his weakened and exhausted state. Merlin's magic pulsed hotly in his chest, and this was one of the many occasioned where Merlin wondered if his magic had a will of its own.

"There just isn't enough time," he cursed and his magic flared again and he suddenly understood what it wanted. Merlin bit his lip and turned toward Arthur. Arthur was still twitchy around him, and he was sure any blatant display of magic would be too much for the king in his fragile state. Thankfully, however, he was asleep with his head tipped back against a tree. If Merlin had had any doubts before, they disappeared as soon as he saw how pale Arthur's skin was and how shallowly his breaths came.

"Alright," Merlin muttered to himself—or his magic; he wasn't entirely sure they were one and the same at the moment. "Do what you have to do."

Merlin was knocked off his feet as an explosion of gold erupted around him. His entire body was tingling as if he had just spilled an entire vat of Gaius' pain relieving tonic all over himself. His hair stood on end and his neckerchief was blown into his face as a strong wind swept through the clearing, obscuring his vision with dry leaves and sparks from the fire. It took him a few seconds, but he quickly realized that he was the epicenter of all the activity. Golden swirls of magic were pouring from his fingertips, and there seemed to be a faint thrumming coming from the surrounding forest. The light and wind gradually escalated until Merlin felt like he was standing in the middle of a tornado on the surface of the sun. Then there was a loud crack like a tree breaking in half and everything stopped even more suddenly than it had started.

Merlin blinked at the center of the clearing they had settled in. Then blinked again. Then jumped when Arthur's voice broke the silence.

"Merlin, I think the pain medicine you've given me has gone a bit off." Merlin finally looked away from the clearing and looked at Arthur, who had been woken from all the commotion, and gave him an incredulous look. A dim part of his mind registered that that was the first time he had called him by his name since Merlin had confirmed his magic a day and a half ago—Merlin was sure that Arthur had been avoiding using it for fear that if he responded to it, there was no possible way that he was actually an imposter.

"Well, I'm seeing two of you, you see," Arthur said, upon seeing Merlin's look.

"It's not the medicine, Arthur. It's just… magic." Merlin turned back to look at what had been occupying his thoughts previously and found his own eyes staring back. In the center of the clearing stood an exact replica of Merlin. In fact, it was Merlin, just from a different point in time. His black hair and ears were identical to the present Merlin; he even stood with the same slumped, but still confident posture that the servant Merlin did. There were only three major differences: first, his clothes were odd to say the least. He wore a long blue tunic, with sleeves that were tight all the way to the wrist, fitted black hose, a cape fastened at the right shoulder, and shoes that barely went to his ankle and had slightly point, curved toes. Second, his mouth was twisted into some sort of grimace. He looked absolutely furious, though Merlin, present Merlin, knew that that was the face he made when he was fighting tears. Third, his eyes, though still stormy blue, were flat and hard and so, so old.

"Oh. It's just, I've never seen magic do anything like this before," Arthur said, his voice surprisingly even, though it was still weak from pain.

"That's because it's never been done before," the Merlin from the future growled. Scratch that, Merlin thought, four things. His voice was deeper and rougher and held none of the gentleness that almost always colored Merlin's voice.

"Then how come Merlin could do it? And who the devil are you?" Merlin closed his eyes for a fraction of a second, wishing that Arthur would just go back to sleep so he could sort this out. Future Merlin opened his mouth, but Merlin decided it would be best if he answered, and beat him to it.

"Well, you see, Arthur," he started, and crossed over to crouch in front of the king. "I…. I needed to find something to save you. So, I let my magic loose and it brought him here." He gestured over his shoulder to the other Merlin, who was standing watching them with narrow eyes. "And as for who he is, he's me. From the future."

Arthur stared at him. He seemed to be trying to decide if Merlin was drunk or insane. But then he looked back at the future Merlin and seemed to decide that unless he was also drunk or insane, the only possible explanation was that Merlin was telling the truth.

"Ok. So, you brought yourself here from the future. With your magic. That you were born with…. I think I'd like to go back to sleep now," he muttered weakly, and let his head drop back against the tree.

Merlin looked at him sympathetically. As if dying wasn't hard enough, Arthur also had to deal with Merlin's secret magic and time travel.

"Just rest for a bit, Arthur. I'll talk to him… uh, me…. And we'll figure out how to heal you," Merlin promised before standing up and walking up to the other man, who had been listening intently. When present Merlin gestured to follow him a little farther away, he turned back to look at Arthur for a few seconds before complying.

"So," present Merlin began awkwardly. He wasn't entirely sure how to talk to someone when that someone happened to be you and had been ripped from his own time stream into the past. He cleared his throat and tried again. "So, what year are you from?" Future Merlin looked him over before replying.

"1168. So, about seven hundred years from now." The younger Merlin cringed.

"So, the crystal showed the truth. I really am…. Immortal?"

"Yeah," Merlin confirmed, but his voice was softer this time. He looked almost sympathetic at the younger man's obvious fear. But present Merlin just cleared his throat again, nodded, and straightened his shoulders.

"So, how do we heal Arthur?"

"We don't," was the curt reply. Merlin's jaw dropped in surprise.

"You mean even after seven hundred years of studying magic you don't know how?"

"No, I know how. But I won't do it." He turned away, looking back at where Arthur was watching them while trying to look like he wasn't. Merlin took a second to process that unexpected turn of events before stepping around the older Merlin to place himself back in his line of sight.

"But you have to. He'll die if you don't!" Merlin's voice was angry—almost as angry as the voice of the Merlin who stood looking at him with flat, cold eyes.

"You think I don't know what happens if I refuse? I know exactly what happens," he snapped. "I know how Morgana comes and frightens away the horses just when you started to think you might actually make it in time. I know how you put Excalibur through her ribs and then leave her body. I know how you struggle with Arthur's weight until you can't hold him up any more and you fall onto the grass. I know how you fight to get back up until he asks you to hold him. How he thanks you for everything you've done while his eyes slide farther and farther away. I know how the last thing he ever hears you say is 'stay with me.' And how you scream when his eyes close until the magic in you fills you and you call Kilgharrah. How it feels to hold onto Arthur's body as it grows colder. I know that you put Arthur in a boat and send it into the lake and how you can't even speak you're crying so hard. I know how you stay for three days and hope you'll die. And I know that you never will." The younger Merlin found it strange that he, who could only imagine all the things that were being told to him had tears streaming down his cheeks and dripping off his chin, while the other Merlin, who had lived them, watched him with a blank face. The future Merlin took a deep breath and whispered one final sentence, as if it was the last brushstroke in his dark masterpiece. "I know, boy, so don't tell me what will or won't happen."

"Then why don't you help him? You can prevent all of that. You can save everything," the Merlin who still had hope whispered furiously back.

"It's been over seven hundred since Arthur died in my time stream. It's given me a chance to realize that the world won't end if he dies. He abandoned me. He didn't fight hard enough. He hasn't come back to me even though I've waited. And now I don't need him. And if I save him for you, everything I've experienced, everything I've learned, everything I've done to help the world, everything I am, will be wiped away. That's why I am refusing to help now, that's why you'll refuse to help when it's your turn."

"So you would force me to endure the same fate, to have the cycle keep repeating, just so you can survive? I never thought I would see myself putting my own welfare above Arthur's," Merlin said with disgust coloring his voice and his head shaking in disbelief.

"It's amazing what seven centuries alone, with nothing but a failed destiny to look back on will do to a person. I will not save him." The other Merlin answered, with the same amount of conviction that Merlin had had only this morning when he was telling Arthur how he could not let him die.

"I can't lose him! He's my friend, my king. Camelot needs him. I need him." Merlin's voice had grown louder in his anger. How is it possible that he could turn his back on Arthur?

"You're Emrys, you don't need anyone. Besides, there will be more kings. And legends and heroes and warriors and diplomats. Arthur isn't the only one," the other man spat back, matching his volume.

"He is to me," Merlin answered heatedly and he practically felt the way Arthur tensed up when he heard the assurance in his servant's voice. The older man looked at him, emotions fighting for dominance in his eyes that were finally being to unfreeze.

"Why?" He asked, without the venom that had been present almost since the beginning of their conversation.

"You know when you meet someone, and they seem so amazing and then you talk to them and there's really nothing special about them at all? And then there are other people you meet and you think "How could someone like you ever do something great?" But then you get to know them and they're selfless, and giving, and loving, and just… amazing. Arthur's the most amazing man I've ever met. And if you don't care enough to save him, why are you still waiting for him to come back?" He had him and he knew it. The Merlin from the future stared at him, suddenly looking so unbelievably tired. He peered over Merlin's shoulder and looked at Arthur for a long time. When he did speak again, his voice was much softer and almost desperate.

"You're asking me to alter destiny, contest fate, defy prophecies, just to save one man?"

"You're Merlin, he's Arthur, and yes, I am. Doing the impossible for Arthur is in our job description."

The older man sighed and ran a hand over his face, then turned and walked back to where Arthur was lying. Arthur watched him approach, his breath coming in short, pained gasps. Their eyes met and Arthur seemed to have lost the wariness with which he had considered him earlier.

"I'm going to change fate for you."

The two Merlin's knelt on either side of Arthur, breathing slowly and in sync. The younger one, the one that Arthur had turned to for an explanation as soon as he had returned—and the other Merlin had forgotten how much he had loved having Arthur turn to him first and how much it had hurt to have Arthur look to someone else for answers—reached up and touched Arthur's hair, smoothing it down as he spoke to him.

"We're going to save you, Arthur, don't worry. I don't know what the spell will feel like, so if it hurts or makes you tired, and you feel like you need to pass out, don't fight it, alright?" When Arthur weakly nodded, both pairs of Merlin's careful hands helped him lay on his back.

Arthur closed his eyes as he felt both Merlins press one hand against his wound and the other on his forehead. The servants took a deep breath in unison and then began to chant, words that seemed to flow directly from the mind of one Merlin to the other. They never faltered or fell out of tandem, pouring golden light into the wound of the king. Arthur dared to open his eyes and saw two pairs of identical molten gold eyes staring back at him.

They worked until they were both spent, repeating the spell over and over without pause. Then, finally, gasping, they took their hands away. Arthur took a long breath and they both perked up hopefully, listening to the steady exhale. They waited for the next breath, both happy to just sit and listen to Arthur breathing for a moment, but the inhale never came.

"No. No, that spell can heal anything. I invented it myself," the older Merlin whispered frantically as the silence stretched on. The other man paid him no heed. He was too busy staring at Arthur's face as it drained of color.

"No! Arthur!" Merlin placed his hands on either side of Arthur's face and gently shook him. "Arthur, breathe. We saved you. We healed you. You can't die!" His breaths were quickly becoming gasps, his voice growing hysterical. Tears started to drip from his eyes again. "Arthur!"

Whether it was the volume of the cry, or the cold tears splashing on his face that roused him, Arthur suddenly took a long, desperate breath. He blinked open his eyes and looked at the identical men sitting by him. The young Merlin suddenly broke into the widest grin Arthur had ever seen, though tears were still falling fast and thick from his eyes. He took his hands from Arthur's cheeks and reached up to wipe at his tears.

"How do you feel?" The other Merlin asked, while the present Merlin dissolved into a slightly hysterical mixture of laughter and hiccups.

"Fine," Arthur replied. "Thank you for saving me." And then, because he was Arthur, he added "No offense, but if I'm alive how are you still here?" Merlin laughed—the first time he had done so in years—and smiled down at Arthur.

"It should be a couple minutes before the paradox catches up. This stunt your servant has pulled is quite a feat. The world will probably be a little out of balance for a while." They both turned to the young man, who had finished pulling himself together and was staring at Arthur as if he had never seen anything so wonderful in his entire life.

"I'll go get you some water, shall I?" He asked, still a little breathless, "I expect you're thirsty." He stood and made his way toward the river that flowed nearby. Arthur watched him go for a few seconds before turning back to the Merlin still by his side.

"So, what happens to you now?" Merlin's heart swelled as he saw the concern in his eyes. Even if he was not the same Merlin that Arthur knew, he was still Merlin, so Arthur still cared for him.

"I will cease to exist. The time line that I live in will be rewritten." When Arthur's face showed hints of sorrow, he added "It is better this way, Arthur. Seven hundred years of solitude is not good for anyone."

"You've waited all that time for me to come again?" Arthur asked, awe in his voice. Merlin knew he did not entirely understand what him coming again meant, but he could understand enough to know how hard that would be. When Merlin nodded, he said "I would never ask that of you, my friend."

"I know. But you'll need me when you get back," Merlin said, smiling sadly. "Just try to be a bit quicker about it this time around. I… He will wait for you, as long as it takes, but that doesn't make it easy." Arthur watched him, as if unable to believe that anyone would wait seven hundred years for him.

"It isn't fair that you had to sacrifice yourself for me," Arthur said. Apparently being brought back from the brink of death made his mind a little scrambled and much more candid.

"To spare a life, a life must be taken," Merlin recited. "Besides, Arthur, I will always put you before me. I just needed to be reminded a little." There were a few moments of silence. They could hear the other Merlin coming back, crunching loudly through the leaves in his haste to get back to Arthur. The Merlin by his side turned to look towards where the noise was coming from.

"His face when you took that breath," he said suddenly, the non sequitur taking Arthur by surprise. "I used to smile at my… you… my Arthur like that. I'd forgotten how it was to have him by my side. I'd forgotten how much I loved that moment when I realized I'd saved him again. Arthur and Merlin, in Camelot, together," his voice sounded wistful. Arthur felt tears prick his eyes in sympathy for the many years that Merlin had been alone, waiting for him. But then the other Merlin came into the clearing and he turned to look at him. When Arthur turned back, the Merlin that had been pulled out of the future was gone.

The ride back to Camelot was mostly silent, Merlin and Arthur riding side by side, because they both seemed to be unwilling to lose sight of the other. Merlin kept glancing sidelong at Arthur, and every time he saw him sitting straight and tall on his horse, his smile grew a little wider. And Arthur was having a hard time grasping the idea that Merlin was a powerful sorcerer that had altered time itself. The time with the other Merlin now seemed like a dream that Arthur had had the night before and was now fighting to remember the details. But one thing stuck out to him as clear as watching a sunrise from the castle walls. Merlin was immortal. And would spend who knows how long of his immortal waiting for Arthur to be reborn or reincarnated or something along those lines. The silence suddenly seemed oppressing.

"Merlin," he said softly. When Merlin turned to look at him the 'thank you' that he was going to say died in his throat. Instead he found himself asking "You'll wait for me?"

Merlin's smile was somehow both sad and hopeful. "As long as necessary, Arthur."