Warning: Spoilers for Episode 1x09 "Excalibur."
Arthur, to his credit, listened very patiently when Merlin appeared in his rooms completely drenched in lake water and babbling some nonsense about a sword.
"Let me see if I understand," he said when Merlin finished speaking and stood by, shivering from the cold and dripping all over Arthur's floor. "Some time ago, you decided that I needed a better sword."
"Yes."
"So instead of going to the royal swordsmith, you went to Tom, Gwen's father."
"Right. Well, sort of."
"And then, for reasons you're not being very clear about–" Arthur took this moment to glare at Merlin, who suddenly looked very shifty. "You then took this sword – which you say is extremely powerful – and threw it into a lake."
"Yes." Merlin beamed at him, obviously pleased that Arthur had followed his odd, somewhat convoluted explanation despite certain suspicious gaps in the narrative and much chattering of teeth.
Arthur stared at him incredulously. "You threw a perfectly good sword into a lake."
Merlin smiled apologetically. "It seemed like a good idea at the time."
Arthur rolled his eyes. "And now you want me to go to this lake and reclaim the sword. Why?"
"Well, it belongs to you. You never know when you'll need it," Merlin said. It may have been Arthur's imagination, but Merlin was looking rather suspicious again. "In fact, you may need it sooner than you think."
"And I trust that you already tried to retrieve it?" Arthur asked, dubiously eyeing Merlin's wet clothes. "What happened? Did you get into the lake and suddenly remember that you couldn't swim?"
"No, well, you see, since the sword was burnished specifically for you by the dragon–"
"The dragon?"
"Er," Merlin said, looking guiltier than ever. "It's kind of a long story."
Arthur sighed. This was obviously one of Merlin's little secrets that he would have to pretend he didn't know about. "Very well. Go on."
"Since the sword is meant for you, you're the only one that can reclaim it." Merlin spoke in a rush, looking relieved that Arthur wasn't going to demand to know more about the dragon but clearly deciding not to push his luck by saying much else.
Arthur gazed fondly at Merlin. "You really are the most incompetent manservant ever, aren't you?"
"Yes, well," Merlin said, grinning and shuffling his feet. "Don't you want your sword? Come on, we'd better hurry."
Feigning annoyance, Arthur allowed Merlin to drag him out of his chair. "Wait a minute," he said, pausing when they reached the door. "Is that all?"
Merlin glanced at him, puzzled. "What do you mean?"
"What exactly must I do to reclaim this sword?" Arthur asked.
"It'll be fine, Arthur, I promise," Merlin said, giving him one of his particularly intense looks that always made Arthur believe everything that Merlin had to say. "I wouldn't let anything happen to you."
After a moment Arthur nodded. "I believe you," he said, and slung a companionable arm around Merlin's damp shoulders. "I was almost expecting you to say that there was some sort of – I don't know – mysterious sorceress of the lake waiting for me."
Merlin smiled innocently. "Well..."