Sherlock sits in his mind palace for an undetermined amount of time until he hears John return. His attention is suddenly drawn to the man stood in the doorway, Sherlock knows he should start this conversation but he doesn't know how.
"I can see your cogs turning Sherlock, you don't need to talk about it," John says as he moves, quite clumsily, towards his seat. Obviously upset and distracted. Sherlock can't just leave him like this.
"I apologise for my abruptness about the topic John, I don't specialise in the area of sentiment,"
"I know Sherlock, I know," John sighs, knowing he's going to get nowhere with the detective in front of him.
"I had no one Sherlock, all my life I had no one and then you just turn up and act as if this whole thing means nothing," John says hesitantly, expecting a snarky remark to fill the empty space.
"John I'm sorry, the whole idea of it.. It scared me," Sherlock says whilst lowering his head, "I didn't want to acknowledge that sentiment existed."
"I was ostracised," snarled John, "Cast aside because I had no one, my own mother pitied me."
Anger now fueled Sherlock, John's little understand irritated him beyond rational thinking,
"Ostracised! You were cast out for not having writing on your arm, what a shame John."
Raising his voice John defended his feelings,
"No one spoke to me as if I was normal Sherlock, you don't get it. They looked at me the way you would an animal."
That opened up a whole floor in Sherlock's mind palace and he was flooded with the memories of his childhood, the nights coming home beaten and bruised. The nights he would avoid eating so his parents didn't have to concern themselves in his affairs. The nights he would take a detour to avoid the knives he knew were hidden in classmates' pockets. With hatred blinding his thinking, he shot up out of his chair and made his way towards the door of 221B Baker Street. Swinging the door open he takes one more look at John and through gritted teeth says,
"Well I'm sorry you weren't normal John."
And with that Sherlock Holmes had taken to the streets of London, leaving the echo of a slammed door to accompany John in his solitude.