Merlin bit at his lip, before finally heaving a sigh. "Arthur, I have magic. I'm a sorcerer."
He refused to look Arthur in the eye. He knew that any second now, Arthur would call him a traitor. Any second, Arthur would order Merlin to the pyre and--
"...Was that supposed to be a secret?"
Merlin's heart stopped. He looked up to see Arthur's face, but he just looked... confused?
"What do you mean? Did you-?" Merlin rushed out his words, watching Arthur closely. He stayed silent, but his expression didn't change, let alone into anger or fear, and that was answer enough. "Aren't you going to - well - kill me?"
Arthur's face lit up in recognition. "Oh. Oh, yeah, no, it's fine. I got through the whole... 'anger' thing when I found out, it's all good now." He nodded, as if to confirm his words.
Merlin couldn't believe it. "When - wait, how - did you find out?!"
Arthur lifted an eyebrow that could rival Gaius'. "You arereallynot that clever, are you, Merlin? It was pretty obvious, you know, when you kept standing - like, two feet - behind me and muttering things in a language I didn't know right before a branch fell on an enemy's head. Plus one of the servants told me."
"How did you notice -what?! Which servant knew? Don't tell me it was Gwen!"
"... I won't tell you?"
Merlin inhaled quickly, gearing up to shout, before he froze and deflated. He lifted a hand to pinch the brow of his nose, muttering, "All the bad things happen to me. I need to stop being so surprised." Merlin pulled the hand away, peering up at Arthur, "So. Just to confirm. I'm not going to be burnt at the stake?"
"Yes, Merlin. Honestly, I know all your secrets, you can't hide anything from me!"
Merlin's eyes narrowed. "I don't think that's true."
"Uh, yeah, it is."
Merlin started chuckling. "You just keep thinking that. Goodnight, my lord."
"No - Merlin, what does that mean-!"