He swam back to the palace as fast as he could, aware that Mycroft's guards must be looking for him already. He had been gone for too long; he shouldn't have gotten so distracted. Stupid, stupid.

His thoughts wandered back to the man again, his mind refusing to think about anything else.

The human had closed his eyes again as soon as he'd opened them, probably trying to focus his vision, and he had used the opportunity to get back into the sea. He was certain the man would think nothing of it. It wasn't as if he had seen his tail anyways, he had merely look at his eyes and, at most, heard his voice, too. There was no reason to worry about any repercussions, he knew. Three days from now, he would be a distant memory, an illusion produced by his semiconscious state.

He couldn't say the same thing about himself, though. He knew he would never be able to forget about the encounter, about how close he had been to a human, to their world. He wanted to go back.

To him, an unhelpful voice added in the back of his mind.

He managed to enter his room without being seen, and he let out a sigh of relief.

"Sherlock. So good of you to be back home."

He stilled, taking a moment to collect himself before turning around to face Mycroft.

"I didn't go too far, I see no problem-"

"Really?" Mycroft said, a tense grin appearing on his face. "How curious. The guards have been looking for you for almost two hours now, and they saw no sign of you."

"It's hardly my fault if they're complete morons. You should probably consider hiring more competent people."

Mycroft hummed, ignoring his last comment. "You see, they found quite an interesting place while searching for you."

He froze up, doing his best to keep his emotions at bay.

"They said they found a small cavern," Mycroft continued. "And you'll never guess what was inside of it."

He remained silent, dread washing over him.

Mycroft's grin faded away, his expression replaced by a bitter glare. "The cavern was filled with human artifacts. Any idea how they got there?"

"None," he whispered.

"Really?" Mycroft said. "They also mentioned they saw someone carrying a human back to safety. Quite an interesting coincidence, don't you think?"

"Mycroft-"

"What in the world where you thinking?" Mycroft hissed. "I have told you, repeatedly, that humans are dangerous. How could you be so reckless-?"

"They are not!" Sherlock said. "You know nothing about them; you have no basis to-"

"You put all of us at risk. If someone had seen you, you could have been captured."

"He was unconscious and there was no one else nearby, it was perfectly safe."

Mycroft clenched his jaw and closed his eyes. When he opened them again, now appearing calmer, he said, "The artifacts found in the cavern have been destroyed."

No. No, no, he couldn't have-

"You will stay in this room until further notice, and when you're finally allowed out, you will be escorted by one of the guards at all times."

"I am not your prisoner, Mycroft, you can't-"

"Yes, I can," he said. "Until you learn to behave properly, you will not leave the confinement of the city again. I'm sorry, Sherlock, but you give me no choice."

And without another glance back at him, Mycroft left.

He drew out a shaky breath, resting his head against the bed.

It was gone. Everything was gone.

Everything he had worked so hard for, his collection...

He clenched his fists, ignoring the lump in his throat. He had to leave. Somewhere, anywhere. He would leave. The mere thought of being locked up, of being stuck in the city, made him want to crawl up the walls.

Then, out of nowhere, a thought struck him.

He sat up, a smile forming on his face.

Moriarty.

He had created a secret exit at the back of his room some time ago, in case of emergency. Escaping through the front door, no matter how late or how deserted the area was, always brought too much attention. Still, he had yet to find a way to leave the city without being seen. All exits were probably being watched by only one man, so if he was patient, he might be able to sneak out during the next shift change.

Half an hour later, he was swimming away from the palace, in search for Moriarty's lair.

While he knew its general location, he didn't know exactly where Moriarty resided. Still, how hard could it be to find?

He had been wandering for twenty minutes, when he saw something on the corner of his eye. He turned around, only to come face to face with an eel.

"Prince Sherlock, I presume?" The eel asked, eyes roaming over him.

"Who are you?"

"You can call me Moran, sir," he said, a sly smile forming on his face. "Are you looking for Moriarty?"

He clenched his jaw, giving a curt nod.

"Follow me, then."

He allowed himself a second to wonder if he was doing the right thing. Was it really wise to trust Moran? It seemed like a ridiculous thought, considering he was after Moriarty, but...

It was the only choice he had left.

He followed Moran until they reached the entrance of what looked like the mouth of a massive skeleton -a Serpentine, his mind supplied-. The entrance lead to a large garden, filled with... were those polyps? He shuddered, unable to suppress the knot of anxiety forming in his stomach.

Finally, they went through a hallway and reached the main hall. It was a room filled with cupboards, with a big conch sitting in the middle. There was also a cauldron in the corner, surrounded by potions and some ingredients.

He tried to get closer to get a better look, but was stopped by a fierce grip on his wrist.

"It's quite rude to go through other's belongings, darling," Moriarty said.

Sherlock cleared his throat. "Apologies."

Moriarty smirked. He turned to Sebastian to whisper something to him, and the eel left.

"So," Moriarty said, getting closer to him, "what can I do for you?"

"I need your help. I want..." He swallowed, looking right through Moriarty's eyes. "I want to be human."

Moriarty's smirk widened. "You've come to the right place, then. But I must warn you, darling - there are some rules you need to take into consideration."

"Of course," he nodded eagerly. "Anything."

"Listen closely, then. This is how it works: I will grant you a pair of legs and you will be able to freely roam the human world for three days. If you want to continue being human, you'll have to get a true love's kiss before the end of the third day... or you'll go back to being a merman."

"But how am I supposed to-"

"You are in love with a human, aren't you?" Moriarty asked, eyes glimmering.

"I'm not-" He cut himself off, avoiding Moriarty's eyes. "How did you know?"

"I have my ways," he answered simply. "Now, what do you say?"

He remained quiet for a moment, thinking it over.

Three days. He had to make the man fall in love with him within three days, and he would be able to stay human. It sounded simple enough, he mused. And even if he failed, he would still get to spend three days in the human world. It would be worth it.

"Do it."

"Slow down, darling, we're not done yet. You don't think I'll do this for free, do you?"

"What do you want?"

Moriarty got closer to him, their faces mere inches apart. "I want your voice."

"My voice?" He furrowed his brows. "But how am I supposed to make him-"

"That's not my problem. The deal is this: You give me your voice as an insurance. If you get your true love's kiss, you'll stay human forever. But if you don't... you'll become part of my collection."

Sherlock stilled. "Collection?"

Smiling, Moriarty turned his head towards his polyp garden. "They used to be mermen and mermaids. That's what happens when you fail at your task."

He took a deep breath. The risk was too high. He couldn't do it, he shouldn't-

He remembered Mycroft's words. He thought about his destroyed possessions, about how he wouldn't' be able to leave the confinements of the city.

If he was going to end up a prisoner, it should at least be on his own terms.

"Deal? Or no deal?" Moriarty asked.

Determined, he looked up, extending his hand to Moriarty. "Deal."

Author's notes:

I'll probably update on Monday, because I'm going to my aunt's for the weekend.

Hope everyone likes this. Please, let me know if you see any mistakes, and constructive criticism is more than welcomed, as always x