A/N: So this is kind of set between Season 4 episodes two and three, except for one small change: Lancelot is alive. Let's say in this universe a random hobo was tracking the party through the dorocha-filled land to the Isle of the Blessed, and after Arthur tried to sacrifice himself and Merlin tried to sacrifice himself and Lancelot tried to sacrifice, the random hobo actually managed to sacrifice himself. I did this not because I wanted to break up Arthur/Gwen (my OTP) but because I needed someone with a brain cell and between the whole lot of them, Lancelot is the only one to consistently have a brain cell (they all shared one brain cell between them and Lancelot took it with him into the Veil and that's why the show ended so badly). This fic has to be after episodes one and two though because of the cut scene in one of them where Arthur gives Merlin his mother's sigil. This is important for reasons later in the fic. I also wanted to pick one of the times Arthur was most likely to be open to magic, and that would be a lot harder with Uther dead given what Morgana did to ruin it.
Merlin trudged through the underbrush, scowling as he stepped over a large fern. "Arthur, I'm sure it's nothing," he whispered. "Can't we just forget it and keep going?"
"We're on patrol, Merlin, not vacation." Arthur crept around the tree, still following the tracks of the "suspicious figure" he had spotted on patrol and insisted on checking out.
Merlin rolled his eyes and resisted the urge to cast a glance back at the knights. He knew they'd be on Arthur's side. Merlin might be too if it he didn't have a strange, tingly, antsy feeling. "Something's wrong, Arthur."
Arthur sighed. "Yes, there is. That's why we're checking it out."
"What if it's a trap?"
Arthur leaned against a tree and turned around to face Merlin. "Then you can cower behind a tree while we defeat the enemy. Now come on!" He shoved off and crept on.
Merlin sighed and followed. Arthur didn't like to listen to him when he had good points. Why would he listen when all he had was a funny feeling? Merlin didn't even listen to himself when all he had was a funny feeling.
Arthur drew into a clearing. He gestured to them. The knights fanned out. Merlin shrugged and stuck to Arthur's side.
A dark figure loomed behind the bushes.
Arthur raised his sword. "Show yourself."
A voice murmured, rising to a shout. "Dod yn ifanc unwaith eto!" The figure raised a hand.
Merlin knocked Arthur down to the ground. The knights charged forward. Merlin panted, struggling to catch his breath. He peeked to his side. The figure had bolted. Arthur was no longer in the line of fire. He climbed off of Arthur. "Are you all right?"
Arthur's clothes lay loose on the forest floor. A small blond head poked out of the neck of his chainmail, blue eyes blinking owlishly. "What happened? Who are you? Where am I?" His lip trembled.
"Arthur?" Merlin exclaimed.
The young boy in Arthur's clothes nodded. "I'm Prince Arthur. What's going on?"
Merlin blinked several times, but the sight didn't disappear. Arthur had been de-aged.
Merlin stood frozen, unable to process or move until tears began to fill Arthur's clear blue eyes. Merlin knelt in front of Arthur. "Hey, hey, it's all right."
"I'm sorry I ran away again, I'm sorry, please don't tell my father!" Arthur's chin trembled. He wiped at his eyes.
"There, there, it's all right, I won't tell your father." Merlin didn't bother to tell him that Uther had been catatonic for a while and wouldn't register his existence. This Arthur clearly didn't have any memories beyond his current physical age. "Here, let's get that chainmail off you." He grabbed the chainmail and lifted it with the pieces of armor and his belt. Given Arthur's new size, they easily slid off without being untied.
When Merlin set the chainmail in the leaves, he turned back to Arthur. He sat in the leaves dwarfed by his gambeson. Tears streamed down his cheeks. He wiped them away with his sleeve. Arthur glanced up, sensing Merlin's gaze on him.
"I'm not crying!" Arthur declared stoutly.
"Of course not," Merlin assured him. He untied the gambeson and set it with the chainmail. Arthur sat in his red shirt, sleeves dangling past his hands and slipping off his shoulders. Merlin tied the strings on the neck of the shirt tight until the shirt wasn't slipping off.
"I'm not! You can't…" Arthur sniffed loudly. "You can't tell my father. Because I'm not."
"I wouldn't dream of telling your father. I serve you, not him." Merlin ignored Arthur's beam that melted his heart, but quickly faded. He folded Arthur's sleeves up until his hands were revealed. He resisted the urge to grab them and marvel at them. They were so small. His arms were stick-thin too. "How old are you, Arthur?"
"Six," Arthur said. "Why?"
"Just curious," Merlin said. "Can you stand up for me, Arthur?"
Arthur nodded. Merlin helped him to his feet, pulling his loose clothes with him. The shirt fell to his knees. Probably modest enough, but Merlin wasn't taking chances with this tiny Arthur.
"What happened? How did I get out here?" Arthur asked.
"How do you think this happened?" Merlin deflected. He pulled Arthur's pants up to his waist, then cinched it tight with his belt that had been around his waist.
"I ran away again with some knight armor and my father's men found me," Arthur said.
Merlin nodded. "Then I'm sure that's what happened." He took the dagger from Arthur's belt and cut off the pants around his ankles. Arthur would have to go around barefoot, but all in all, he was semi-presentable. He tucked the dagger into his own belt and sat back.
Arthur was quite small for a six-year-old. He was also quite pale and skinny, almost sickly. He was still sniffling. "Why don't I remember all that?"
Merlin frowned. "Because you were attacked by a sorcerer. The knights are chasing him down now."
Arthur nodded. He wrapped his arms around himself.
He was so trusting. Older, normal Arthur was plenty trusting, but this Arthur… he just believed what he was told without question.
"Who are you?" Arthur asked.
"I'm Merlin."
"We lost him," Lancelot said. The other knights crashed through the underbrush behind him.
Arthur jumped and spun around.
Gwaine frowned. "What happened to Arthur?"
Merlin stood and put a hand on Arthur's shoulder. "This is Prince Arthur Pendragon."
The knights stared at him in silence for at least a minute.
"That can't be," Percival said. "Arthur is—"
"Lost in the woods?" Merlin broke in. "We need to get him to Camelot as soon as possible so he can recover from his magical attack, don't we?" For some reason, he had an urge to protect this tiny, trembling Arthur far more than he protected his adult friend.
The knights stared at him in shock before Leon broke free.
"Of course." Leon stepped forward. "We should return to the horses and ride for Camelot." He set off through the trees.
The other knights followed. Percival stepped over to grab Arthur's abandoned things.
Arthur pressed close to Merlin's legs. Merlin patted his shoulder and led him forward. "It'll be all right."
"I'm not scared," Arthur murmured.
"Of course not," Merlin agreed.
A/N: So instead of old English, I used Google Translate Welsh because I'm lazy.
This fic is all written, so if I forget to post, just holler at me.