The boy grinned at the look on John's face when his friend genuinely disappeared into the tree trunk. He got up, and jogged over to the tree, peering in himself. And gasped when he, too, saw the inside of the flat, with Sherlock standing in the middle of the living room, frozen, eyes darting every-which-way as he was assured beyond a shadow of a doubt that he was really here.

"What-how-" he whispered.

"Simple," said Merlin, poking his head into the tree behind John. "Magic."

"Magic cannot possibly exist," the detective retorted.

"Why?"

"Because it is a fantasy created by people with fanciful imaginations."

"Then how do you explain being in your home, with the entrance being a tree?"

"Because it-because you-"

Sherlock scrambled for an explanation, but finally had to concede that no matter how improbable the situation, it had to be the truth. Magic was real. And it had just been used to open a portal through a tree to Baker Street.

Merlin made a satisfied sound, and then turned to John.

"We should bring Arthur in now. Quickly, before someone sees this."

"Oh-okay." John hurried over and helped him lift his friend (who had drifted off to sleep), bringing him into the flat and gently laying him down on the sofa. They pushed the boat back out onto the lake; it seemed unlikely to serve any useful purpose to bring it in. However, Merlin did collect the remains of the chain mail and Arthur's shirt, by bundling them up in the red cape. And John retrieved his medical kit. As soon as they were all inside the flat, Merlin muttered in that language again; his eyes turned gold, and the entryway closed, leaving not so much as a seam in the wall.

Sherlock finally forced himself to adjust to the situation. So there was magic in the world. So a few of his accepted simple truths had just been turned on their heads and given a shakedown. So King Arthur was lying on his couch, and his famous wizard (sorry, warlock) Merlin was standing by the bookshelf, examining the titles. He could deal with it. It might take a little more time, but he could deal with it.

John checked Arthur's vitals again, and announced, "He'll live. He needs rest, and to be kept warm and given plenty of fluids...but he'll live. And actually, it might be better if I stitched the wound now." He knelt down, and set to work. These weren't the best conditions for it, but it wasn't the first time there'd been blood on the sofa (long story), and more than likely it wouldn't be the last. At a gesture, the two other men began assisting him.

While they worked, Sherlock abruptly looked at Merlin and asked, "Who's Gaius?"

The younger (well, actually much, much older, but he looked younger) man looked down, and murmured, "My father." Then, after a second, he amended, "Well, you could say he was actually my stepfather. But he was the closest thing to a father I had for most of my life. So he deserves the title."

Sherlock could sense, based on his choice of words, that Gaius was dead. But something prompted him not to confirm his suspicions (for once). He just continued helping John.

Arthur must have been truly exhausted, because he barely acknowledged the fact that he was being operated on. And as soon as he was stitched up and the wound was bound, he just snuggled further into the couch, and seemed to go back into a deep sleep. John shepherded the others into the kitchen to clean off their hands, and once they were clean, he began making tea.

"Care to tell us what all this is about?" he asked.

Merlin sighed, and leaned against the counter.

"It's a very long story," he explained.

"Well, Sherlock will never forgive you if you leave without satiating his curiosity. So you might as well start telling us."

The detective gave John a look, but he just stared back as if to ask, 'Can you deny it?' And he was forced to shake his head no, and gesture to Merlin impatiently.

Merlin told them everything that he felt was pertinent: about how he first came to Camelot, how he became Arthur's manservant, his having to hide his powers for most of his life because if anyone found out he'd have been executed (Sherlock did interrupt there, to point out that if he was so powerful, couldn't he have just used his magic to protect himself if anyone found out? Surely even if they threw him in a dungeon, he could just escape. Merlin, after an awkward moment, just said that it was difficult to explain, and moved on.), how Morgana had gradually turned evil and tried to destroy Camelot, how Mordred eventually gave Arthur a fatal wound, and how Merlin put him on the lake, where the Lady of the Lake would protect him until he was needed again.

"...And you've just been waiting for him all that time?" John asked, sipping his tea (which he had finished while Merlin talked).

The warlock shrugged. "Basically, yes. Normally I look a lot older, but I found a spell to make myself look like I did when Arthur knew me-I wanted him to have something familiar to-to help him feel more at home."

"Awfully nice of you," Arthur murmured, staring at them over the back of the sofa.

Merlin muttered something about the infernal region, and then demanded, "How long have you been awake?!"

"'Bout when you were telling them about Morgana…" His expression became sad for a moment. Then he said, "That smells good," pointing to the tea.

"It is," the warlock agreed, sipping it.

When he realized that the man he still thought of as his manservant had no apparent intention of giving him a cup, Arthur sat up a little straighter (flinching as he did so from the pain in his shoulder) and asked, "Would you be so kind as to give me some?"

Merlin glanced over at John. "Is it safe to let him have a cup?"

"It's fine," the doctor reassured him. Satisfied, Merlin poured a mug of tea, and brought it over to the former king, who happily began to drink.

"At least they know how to make a decent cup of tea around here," he murmured finally. "Though otherwise, this place is just...weird."

Merlin flinched at his friend's bad manners. Arthur didn't notice. He just watched the two other men who joined them in the living room with curious eyes.

"You never answered my question, Merlin-where are we?"

The warlock said promptly, "It's called London."

"London…never heard of it. Is it close to Camelot?"

"Sort of."

Arthur looked around, paying special attention to the electric lights, the tiled kitchen, and numerous other things that wouldn't have looked strange to anyone else.

"Merlin, is this-does this place have magic?"

"No, it's science," Merlin reassured him. "You know, like Gaius was always doing."

If he hoped to satisfy Arthur, he failed miserably. The blond man started shaking his head emphatically.

"No, no, Gaius never did anything like this. There's something you're not telling me, Merlin. What is it?"

Merlin swallowed, looking away uncomfortably. Arthur gave him a confused stare, but then looked to his companions.

"How far are we from Camelot? I need to get back there as soon as my wound is healed. Or even sooner, if possible."

John and Sherlock looked at each other; Sherlock raised his eyebrows, as if to ask, Should I tell him?

John glared, and shook his head. No, you idiot! Are you out of your mind? Do you know what that knowledge would do to him?

He's going to find out sooner or later, the detective implied, with his 'surely this is obvious, John' face.

John's forehead wrinkled. He just had surgery on his arm and shoulder. I don't think he's in any condition to learn about this.

Sherlock was about to argue (verbally) that since the man was obviously a trained soldier, based on the callouses on his hands and his arm musculature, and based on the fact that he was already awake and talking, he probably had pretty strong adaptive abilities, when Arthur interrupted by banging his mug of tea down on the coffee table, nearly breaking it.

"I am the king of Camelot, and I demand to know-"

"You're not the king anymore!" Merlin interrupted.

After a shocked moment, Arthur turned his head towards his manservant.

"What?"

His voice was a combination of anger and confusion, though his tone was soft.

"Arthur-I'm sorry to put it like this, but Camelot doesn't exist anymore."

Before Arthur could start asking questions, Merlin hastened to reassure him, "Morgana and Mordred are both dead, so it wasn't them. After you-after I put you on the lake, Gwen became ruler of Camelot, and it all went well-but it's been years. Centuries, actually. And, well, you've been kind of asleep for all that time."

Arthur blinked, slowly. Finally he asked, "Centuries?"

"Yeah." Merlin reluctantly told him the year; Arthur promptly turned white.

"So-so Gwen and Leon and everyone-"

"Yeah. I wasn't going to tell you yet, but I guess I have to. They're all gone. Everything's changed." Merlin sat down quietly, pain in his eyes. "I'm so sorry, Arthur."

The erstwhile king of Camelot rolled onto his side, turning his face into the couch.

Sorry, I know it's been a while. I was kind of stuck about how to write the next part. But I hope you liked it.

I don't remember if they actually had tea in Merlin, but let's say just for argument's sake that they did. Let's also say, just for argument's sake, that Arthur was asleep for all the time he was with the Lady of the Lake, so he doesn't know about how much the world has changed while he was gone, or that everyone else is dead. Which, while I'm thinking about it, would actually be pretty horrible. Kind of like for Captain America, only on an even more extreme level. I'm babbling, aren't I? Sorry.