"John," Sherlock called calmly from kitchen. He waited. There were no footsteps indicating that John had heard and was coming. "John," he called more insistently.

John had heard. He was upstairs in his bedroom, but he had heard. But John was tired of Sherlock's shenanigans, and didn't want to indulge another one of his 'look at the rotting flesh' experiments or 'can I use this riding crop on you?' tests. So he ignored him, and resumed reading the not entirely fascinating medical journal Sarah had given to him.

"John," Sherlock called again, with an edge of panic in his voice.

John gritted his teeth, throwing down the journal and swinging his legs over the side of his bed.

"This had better be worth it!" he bellowed.

There was no response and John padded down the stairs to find Sherlock sitting at the kitchen table, bunsen burner going, staring off into space.

"For gods sake-" John reached over and turned the flames off, "if you're going to go to your mind palace, at least have the decency to not burn down the flat."

Sherlock continued staring blankly into space. He didn't seem to be looking at anything, which usually meant he had completely zoned out.

"Well?"

"Well, what?"

John sighed. "What did you summon me for, your highness?"

"Oh, that," Sherlock waved a hand dismissively. "I seem to have gone a bit blind."

"A bit blind- are you serious?!" John stared open mouthed at Sherlock, pausing before waving a hand in front of his face.

"First, yes. Absolutely. Second, I can feel the breeze from your hand," he reached out and grabbed John's waving wrist as he said this. "And third, which you haven't asked yet, I was doing an experiment."

"What the hell kind of experiment were you doing that made you go blind?!" John snatched his wrist away from Sherlock as he demanded an answer.

"I was burning magnesium," he gestured towards small piles of ashes sitting in crucibles near the now extinguished bunsen burner. "It burns very, very brightly," he added, in a kind voice for John's sake.

"Yes," he snapped. "I did do chemistry thank you very much."

Sherlock shrugged, as if he was saying well, I deal with so many stupid people every single day I forget that you're marginally cleverer than most of them.

"So why the hell did you look at it!"

Sherlock replied patiently, like talking to a small child, although, John suspected, Sherlock did not do well talking to small children. "To see if it could make me go blind."

John spun around, stalked into the living room, and threw himself into his chair. This was too much, too early.

He rubbed his tired eyes. "So, let me get this right. You wanted to make yourself go blind."

Sherlock nodded impatiently.

"Right, cause that's bloody useful," John muttered.

"Blind, not deaf," Sherlock pointed out. "Should be temporary. Although it would likely be best if you assisted me to the couch and retrieved my violin for me. You tend to rearrange the flat frequently." He frowned. "Also, I was doing some experiment yesterday that involved explosions, and my hearing is a bit off, which is affecting my balance." He turned towards John. "So?"

John got up out of his chair, reaching Sherlock in the kitchen, and roughly steering him towards the couch that he would live on for days on end when they did not have a case.

"Sit," he ordered him. For once, Sherlock obeyed. "Where is your violin?"

"Bedroom. Closet. Top shelf." John turned to head off, but only got a couple of steps before Sherlock called "Oh and be careful when you open it. It is a bit precarious."

And sure enough, when John tentatively opened the door to Sherlock's closet, a number of things almost fell on him, and would have if not for the warning. Nothing breakable, he noted, which was good. But... was that a human thumb? He shook his head. John couldn't quite reach the top shelf, so he grabbed Sherlock's desk chair and pulled it over to stand on, ignoring the thumb on the floor. The violin was indeed on the top shelf. He pulled it out, purposely leaving the chair where it was to annoy Sherlock.

He carried the violin back out to Sherlock, who had assumed his classic thinking pose on the couch. Lying down, fingers steepled beneath his chin, eyes closed, presumably deep in thought. John set the violin down on the table next to Sherlock, and returned back upstairs with his laptop in tow to research how long the blindness would last resulting from staring at magnesium.

He hoped it wasn't long.