Chapter 1: John

When John walked through the door the first thing he thought was 'bad Sherlock'. The whole hallway smelled and he was glad that Mrs. Hudson wasn't in yet so that he had time to air the hall. He classified it as not being a nice smell but if he had to describe it, he wouldn't be able to name anything that had a similar smell. After opening the windows on the ground floor he walked up the steps. John nearly fell back when he was confronted full force now with the smell, no door in between anymore blocking out the worst of it. He held his breath and ran to the window opening it quickly and doing the same thing with the second one. With his head hanging out of the window John took a deep breath and remembered how normal London air was supposed to smell.

A noise let him turn around but what he saw was not something he had expected or ever expected to see in this flat. There was a child, a toddler, not older than three who was looking at him with huge, shy eyes from behind the sofa. 'Did Sherlock kidnap a child?' No he wouldn't, would he? John wasn't too sure about it.

"Hallo, little man, where did you come from?" The child was still looking up at him but didn't answer. Maybe it was scared. "My name is John, what's your name?" The child looked a bit uncertain as it slowly stepped out of his hiding place.

"William. My name is William. And I don't know where I am. This isn't my home." John feared the child, William, would start to cry but it looked around the flat with curiosity.

"William, have you seen my friend? He should be in this flat too. He is very tall and has black hair, like yours and…" John stopped. The child wasn't listening to him anymore. He had found the skull that was on the small table next to Sherlock's chair. With his small feet padding the boy walked over and touched the surface of the bone.

"It's a skull. Part of the human skeleton." Said the boy too busy touching the bone to see John's face.

"That's right. How do you know that?" John wasn't sure normal children at that age knew things like that or words like skeleton.

"My big brother has a book on an… antoi… anatomy." That was a big word for a small boy. "He explained it to me and answered all my questions. My brother is really smart and always explains everything to me." The little child smiled at him. As a sudden tummy rumbling distracted him again.

"John, I'm hungry." John smiled at this.

"Let's have a look in the kitchen. We should have toast and jam." As John was about to turn towards the kitchen William stood with his arms open in front of him. "Do you want to be picked up?" It was the only explanation he could come up with and a nod from William confirmed it. "Okay, come on." He lifted the little boy up who held tightly onto John small hands fisting into his shirt.

John placed William on a chair at the table, as far as possible away from the lab equipment, prepared toast and a glass of milk for the boy. He placed it in front of the child who started happily to eat. John watched him until he found a letter between the microscope and the Bunsen burner. A letter with his name on it. John took it and started to read.

Dear John,

If my experiment was a success you should be in the company of a child right now. Don't panic. This child wasn't kidnapped and I didn't perform an experiment on him. It's me. My younger self.

I read an article in a science journal about a formula that lets your mind and body age backwards. In this case it should be around 30 years if everything worked perfectly. The effect should keep me in the body of a child for around a week maybe two.

Please keep an eye on younger me. If I'm not too much trouble, please take a few notes about my behavior so I can compare them with the real me from my childhood. Pictures would also be much appreciated.

To confirm it's me you can ask Mycroft. He will also provide you with everything my child me will need.

See you in a week or so.

Sherlock

P.S. Mycroft has to bring Mr. Bee to me; he will know what you mean.

John read the letter more than once before he risked a look at the child next to him again who was still eating his toast with jam. Although the jam seemed to be everywhere except in his tummy. A lot of feelings came up in him going from anger to disbelieve and fascination. Did Sherlock really let himself regress just to confirm his experiment? Was his mind really that of a child or was he acting like that for John? But the adult Sherlock would have never asked for food and then eaten it like that.

"Sher… William, can you tell me your whole name?" He asked carefully, the child swallowed the last bite of his toast with milk before he answered. "William Holmes." Not the answer John had hoped for. "I mean do you have a second name like me? My name is John Hamish Watson." The child giggled. "That's a funny name. I have two second names. William Sherlock Scott Holmes but I don't like Scott and Sherlock sounds a bit ridiculous." John nodded; the probability that the child really was Sherlock had risen dramatically.

"William I have to call someone… would you like to draw a picture for me?" It was the only thing that came to his mind right now that children did to busy themselves. "We can put it on the fridge so everyone can see your beautiful picture." Little Sherlock was happy, jumped down from the chair, took John's hand and pulled him to the living room. John collected a few different colored pencils, a few sheets of paper and placed everything on the table. As Sherlock started to draw he took a picture and sent it to Mycroft. He had to wait only two seconds before his phone rang.

"Hello Mycroft how is your day?" John put all his sarcasm in his words because he wasn't looking forward to minding a child for a whole week. The thought had only occurred to him the moment he had sent the picture. He had no experience with children and even less with a genius child who probably would need special attention.

"What did he do?" Mycroft sounded more than tired. Sherlock had mentioned that Mycroft was trying to make a deal with some country; one reason why he had brought him a case and Sherlock had just accepted it without fight. Mycroft must have been really stressed. It was probably more than one country or one deal. But as the British Government you sometimes (or often) had stress. That his baby brother was now a real baby wouldn't help.

"Oh I don't know exactly. Some sort of experiment which means I have to babysit him for a week. He asked in a letter that you bring Mr. Bee - whoever that is - and everything else his child-self needs. By the way, when did he start to use Sherlock as his name? Didn't know his first name was William" While talking he watched Sherlock, no William, drawing something that looked like a flower. He had to smile at that.

"I will come over with everything. Keep him busy until I arrive. I need to finish something here." John ended the phone call before Mycroft could do it and let out a sigh. How on earth should he deal with the little version of his friend? John turned to make some tea to relax or think or to just do something else when the noise of falling pencils got his attention.

"Don't leave me alone." William was already hugging his leg with all of the strength of a little child.

"I won't, I will just make a tea. You can come with me if you want or keep coloring." William didn't let go until John picked him up and William was secure in his arms while he started making tea.