Merlin hears the door open, but doesn't look up from where he's making up the bed. He hears Arthur say his name, and he notes that the king's voice sounds different, heavier than usual, but brushes it aside as a rough day.
"I was just about to fetch your dinner, but I saw there was a hole in your blanket and I knew you'd be angry if I just left it so I-"
"Merlin."
Merlin lifts his head, and is immediately shocked to see Arthur standing in the center of the room, sword half lifted. He's shaking.
"Why have you got your sword out?" He asks.
"Merlin, you have to get out of here." Arthur's voice is desperate and shaky. Something's gone wrong.
"Why? What's going on?"
Arthur suddenly jerks forward, his foot flying out, dragging his body with him as if against his will. The king stumbles.
"Just go, Merlin, I don't have time to explain, you have to leave-"
Merlin straightens up, eyeing the stiff way Arthur's holding himself, as if he's running and staying still at the same time. His sword is raised, pointed towards Merlin, and Arthur is breathing hard, sweat shining from his forehead.
"Just tell me what's wrong, I can help you," Merlin says, going around the bed to approach Arthur, but Arthur jerks and shouts:
"Get away from me!"
Merlin freezes, raising his palms up in surrender.
"What's gotten into you Arthur? What's going on?"
"I can't control it, it must be some kind of enchantment, and if you don't run it's going to make me kill you, so you have to run."
"What?"
"You have to run, I can't control my body and I won't be able to stop myself and if you don't run right now I'm-I'm going to-the magic is too strong, I can't fight it for much longer-"
As Arthur speaks, his body jerks forward several steps so that the sword nearly impales Merlin, but Merlin dodges it and steps away hastily.
"Arthur, what happened? What kind of enchantment?"
"I don't know, there was a girl, I thought she was a serving girl but-but she spoke some words and then-then I was walking here, against my will, and then I had my sword, and-I can't stop it, you have to run-"
Merlin's breath speeds up to match Arthur's ragged inhales. The magic is strong, he can feel it's presence in the room, a dark magic battling with his own. It's taking over Arthur, even as he stands there trembling, feet braced on the floor but stumbling forward. The magic is trying to force his body to move, and Arthur is fighting hard to keep still, but the magic is too strong...
"If I leave you, you might turn on yourself."
"No, don't think about that, go find Giaus, or something, but now you need to run-"
Arthur is cut off by himself lunging forward, raising his sword and attacking, and Merlin ducks, nearly missing a sword through the head. He runs behind Arthur, and Arthur turns to chase him, sword poised. Merlin finds himself caught in a corner, and turns to find Arthur advancing, face strained and limbs jerking. Merlin braces himself for death, but Arthur gains control for a moment, stopping just when the sword is inches from Merlin's chest.
"Run," Arthur pants, his eyes wild, "Run, Merlin."
Merlin looks into Arthur's eyes, pupils blown wide and terrified. He doesn't want to leave, he has to find a way to stop this-
"RUN!"
Merlin does.
AN: I was planning on just getting this idea out of my head, but I guess if enough people want me to continue it I will!
