Nicotine

Because

Sherlock walked up the stairs to the flat, footfalls heavy. Case closed. He yawned, tired.

It was late, somehow it always seemed to be late when he went to sleep. He unlocked the flat and came in quietly- John would have gone to bed hours ago. He chucked down his keys and stretched slowly. He felt a familiar ache in his ribs, still lingering on over a month later. He slipped off his jacket and turned on the lights.

John stood besode the desk in the living room, unmoving. His back to Sherlock, he was holding something. Sherlock frowned.

"John?" Sherlock asked cautiously.

John turned around slowly. Sherlock's eyes widened.

"Explain. Now." John demanded.

Sherlock stared.

"I-I-"

"You better come up with something good because this is the last straw." John said darkly.

"An experiment." Sherlock said smoothly, transfixed by the all-too-familiar needle in John's hand.

"On yourself I suppose."

"No, I was-"

Sherlock stopped dead as John hastily rolled up his left sleeve. He positioned the needle over his arm.

Sherlock gulped.

John squared his feet.

"John, put the needle down please." Sherlock said slowly.

"No. What is it anyway?" John said, looking at the little syringe in his hand. "Heroin?"

"Yes- no, it's a- a mixture. Please-"

"Jesus Sherlock, oh my god. What...?"

"Acid too." Sherlock whispered.

John examined the veins flowing up his arm and poised the needle more accurately.

"I'm not an addict, John. I'm not. Just sometimes, I need-"

John raised his eyebrows. "You need?"

"Need, yes. An escape."

"We can do this slowly and I can lower this needle or you can hurry up and I won't."

Sherlock fought hard to stay calm.

"An escape from everything. My mind. My brain is like an engine, burning itself out and tearing itself apart piece by piece. I need distractions, always more distractions. Cases normally fill that role. There's not always cases." Sherlock said shakily.

"So this is what you do instead?"

Sherlock's hand shook as he reached out towards him. He took a step forward but John only lowered the needle.

"Please John." Sherlock whispered. "Stop it. Stop...this."

John's face remained set but his hand wavered.

"Put- put the needle down, John."

"I AM NOT FUCKING PUTTING THIS DOWN SHERLOCK!"

Sherlock's eyes widened and his face drained. He still had one hand outstretched.

"Don't do this please don't do this I can't -you can't-" Sherlock's voice cracked.

"Why are you doing this to yourself Sherlock?!" John shouted.

"IT DOESN'T MATTER ABOUT ME, JOHN! IT NEVER HAS." Sherlock yelled desperately.

"You'll kill yourself." John said.

"No I won't." Sherlock replied, dismissing John completely.

"Sherlock, I'm a bloody doctor. Tell me, what is going on? Why now? You hadn't taken anything for ages, you were doing really well. Why relapse now?"

Sherlock answered slowly and looking at the needle, not John.

"Because I can't bear my emotions."

Silence.

John stared at Sherlock, needle momentarily forgotten. "I thought you didn't have any."

"I try John, believe me, but my thoughts betray me. I separate myself from feeling anything but..."

"What?"

"It's so difficult." Sherlock whispered.

"So this is your alternative." John said angrily, waving the needle around. "You decided that it's okay to stick needles in your arm instead. What do I think? You're a fucking idiot. It doesn't solve anything."

Sherlock had no answer.

"What would happen then, if I took this?" John asked, repositioning the needle over his arm purposefully.

"Pain," Sherlock said hoarsely. "And then nothing. Just...nothing. A break from your thoughts and feelings. Then after a while, but never long enough, your head begins to throb and your mouth is dry and everything is sore."

John pressed the needle onto his arm.

"DON'T!" Sherlock half-screamed, his voice cracked and terrified.

"You do it. You said it was an escape. First, I think you kill yourself in front of me. Then, as I'm getting engaged, as I'm proposing, you show up out of nowhere. Just as I'm starting to manage it all again, my pregnant wife is shot dead. Instead of being allowed to mourn her in peace I read a file that makes me despise her. You're in Madrid and I'm left alone. You come back, and it's kind-of okay. Sometimes we talk and it's like before... before you even...before the Reichenbach. Mostly we don't though, and sometimes we argue. Then, I find these and I find out you're practically killing yourself when I'm not looking. What makes you think I  don't deserve an escape?"

Sherlock stared.

A bead of blood escaped from John's arm at the base of the needle. His hand shook as his thumb shifted to the plunger.

"Stop John- please stop I can't, you can't, it's not okay- I'm not okay you're right I'm sorry...stop it. Please put it down please."

John paused.

Sherlock took a shaky deep breath.

"It's been because...because...because I love you, John."