"Why on earth were you out this late?" Gaius asked, with the countenance of one who liked people to say things outright so that he could make them properly ashamed of themselves. "I thought this supposed difficult choice of yours meant I didn't have to worry about you for once, not that you would lie to me and sneak out again!"

Merlin knew he should make some sort of joke to lighten the mood, but as his own mood was rather dark, he settled for asking, "You were worried?"

Gaius fixed him with a disapproving gaze, but it faded to something like concern after Merlin lifted his head to look at him. He imagined how pitiful he must look for him to actually show that much concern. Gaius didn't smile as he said softly, "I always worry."

"Sorry." Merlin glanced down at his hands, long and pale and streaked with mud, and waited for Gaius to ask unhelpful questions that he had no way to answer.

A long silence hung in the cold air between them, and in surprise, Merlin realised that he was waiting for him to speak first. It was refreshing, and he found that he preferred it to Arthur's way of drawing whatever he thought the problem was out of him and never letting him speak of it again. He took a moment to think about how he would explain the situation, surprised that he was given this moment instead of the off-the-cuff excuses he usually relied on.

"I either did something very right or very wrong tonight and I'm not sure which."

Gaius set a candle on the table between them and Merlin lit it with a glance, illuminating the lines around his eyes and his firmly set mouth. "What do you mean?"

"Arthur freed the boy." At a quirk of Gaius's eyebrow, he elaborated. "I wasn't planning on doing anything to help, but..." he trailed off with a sigh, remembering the panicked cries that had resonated around his skull and the ache of empathy in his chest.

"The boy started pleading with me - in my head - to save him, and I couldn't stand by. Arthur, Morgana, and Gwen would have hated me, the boy would have died needlessly, and all this would have happened because I was a coward who trusted the wrong sources."

Merlin immediately realised his mistake, but before he could talk his way out of having to explain that as well, Gaius asked him, "What sources are these?"

He remembered Gaius telling him about the dragon as if it were something not to be spoken about rather than to be consulted, and decided against telling the truth about his source. He shifted in his wet clothes, focusing on the rust on the candle's holder and the wax slowly melting in the centre of it to give himself time to think.

Wondering how to answer and coming up with nothing, he decided upon a vague, "They prefer to remain anonymous. Well, I prefer them to remain anonymous. I don't think you'd approve, but I swear to you that he isn't likely to put me in any kind of danger I wouldn't get myself into anyways. I only ask him for help when I'm out of options, and he does give help, even if it doesn't always seem helpful."

Gaius gave him a stern look, but it softened into curiosity again. "I had thought as much. Why wouldn't you have freed the druid boy?" He inquired gently.

"My source told me that he would grow up to do something unthinkable. I didn't want to believe it, for obvious reasons, and because it meant..."

Merlin ran a hand through his damp hair and shivered. There was something tight and anxious in his stomach that he couldn't seem to get rid of, no matter that he and Arthur were both safe for the time being.

"It would have meant that no one could escape their own destiny. I can't believe that. But I couldn't aid him because of this unthinkable thing."

He gazed up at the instruments hanging from the ceiling, lit by the faltering light of one candle. Gaius watched him knowingly. "You freed him anyways?"

"And I spent a full hour hiding from guards in the forest, in the rain, thinking about my mistakes. I wouldn't recommend that." Merlin gave him a rueful smile. "Arthur trusts me now, and I can't betray that. I know what it's like to face execution for something you can't help. I can't let people die who I can save. He was a child, Gaius."

Gaius reached across the table and captured Merlin's hand in his gloved, aged hand, something in his eyes that looked almost like respect. "I have been in your place too many times, and you did a much better thing than I did in that position."

He remembered with surprise and some guilt that he was not the only one who had made difficult choices. There was only compassion in the lines in Gaius's face, and for the first time, he felt that he truly knew why his mother had sent him to Camelot. He would have given anything for this kind of mutual understanding when he had been alone and scared.

Gaius had become his only confidant, and though they seemed to exasperate each other frequently, he knew that they both had needed someone who understood them. He squeezed Gaius's hand back, and silently thanked his mother for sending him away.

Quietly, Merlin confessed, "The boy will kill Arthur one day."

The moment hung in the air for too long, as Gaius's jaw dropped and his eyebrow shot up in undisguised alarm at the very thought of the boy living to kill Arthur. His fingers went stiff and clawlike, still gripping Merlin's hand.

Self-conscious and sensing questions, he added, "That's what I was told. I don't know if I did the right thing - I don't know anything anymore. Just -"

Gaius glanced towards the door in search of eavesdroppers, then back at him, his eyebrows expressing his shock with an eloquence Merlin had rarely seen. He exhaled quietly, then looked back up at Merlin, speechless.

"If my destiny is to protect Arthur and Mordred's is to kill him, then my only choice is to kill the boy." Merlin shivered again, refusing to entertain the thought. He glanced up at Gaius, found himself unable to look him in the eye, and settled his gaze on their hands. As he spoke, he drew his arm back and curled into himself.

"I don't want to become a slave to a destiny I barely understand. I won't be a murderer unless it is absolutely necessary. I can't make myself into a pawn for the dr- my source's little chess game."

He put his head down on the rough table and sighed, hating the choices he had made and would have to make. "I don't remember feeling this helpless before I came here."

He allowed himself a short amount of time to feel frightened and frustrated, to remember that exactly how close in age he and Mordred were. If his mother had given him to the druids as she must have considered after his birth, they might have been friends. The boy was innocent, and he was supposed to turn himself into a monster for a cause supposedly greater than himself.

Gaius sighed in empathy, and Merlin imagined him shaking his head. "I advise you watch and wait. If Mordred comes back and harbours ill will towards you or Arthur, you will have to act in some way, but if he never appears or if he has good intentions, you may not have to act at all."

Merlin raised his head and protested, "But my source was so sure that it would be a mistake to help him! He's wiser than I am, and his advice has served me well before. He's a bit cryptic about it usually, though, and this boy is the only thing he's been absolutely clear about so far. I don't know much about him, but he hates Uther, and I doubt he's selfless enough to give advice that benefits anyone but himself."

With a worried, slightly grim frown, he advised, "It sounds as though you need to exercise caution in dealings with this source of yours."

He nodded to himself, remembering the dull gold gleam of Kilgharrah's smile as he murmured, "I'm beginning to see that, yeah."

Gaius gave him a look of warning, setting his hands down on the table in front of him and leaning in. "Merlin, you may be powerful, but you need to know who to trust. Some of the people you may have to have dealings with may not be ones that you trust, and I understand that, but you must always be careful."

"You know me," he said cheekily with no conviction.

"This isn't a joke," Gaius reprimanded him, genuine concern in his eyes. "I would not have to warn you this often if you were careful."

Merlin nodded, glancing down at the table in shame. "I know. I'm sorry."

"You're not sorry enough that you'll stop scaring me half to death," he replied with a significant look, and snuffed out the candle. The lines on his face made him look positively ancient in the moonlight filtered through the windowpane. "I'm going to bed. I expect you won't be going out again."

"No," Merlin muttered, and sighed. "I think I've learnt my lesson here."