In this, there are mentions of drug use. Also, it is a little shorter than normal, but I will make up for it in the next part. And I know that this part is mostly John, but it is really a Sherlock imagine, and he will be in the next chapter. 

John raced through the streets of London, as fast as his legs would carry him. If he was thinking straight, he would have hailed a cab. But he wasn't. All he could think of was what he had seen. All he could think of was his friend. All he could think of was getting to (Y/n). After all, this was all her fault. No, that was cruel, John managed to think, as he continued to run. (Y/n) had put up with so much. She had given Sherlock nothing but love. She had taken care of him. And all Sherlock had given in return was ambivalence and ingratitude.

John hadn't been able to believe his ears when Sherlock had told him that he had a woman in his life. That he had found someone that he didn't dislike as much as he did the rest of the human race. And John had been able to believe his eyes even less, when he had finally met said lady. When he had met (Y/n). It had been obvious to him, Mycroft and Greg, that she was too good for Sherlock. That she was far too sweet, loving and kind to want to have anything to do with a man, that even on the best of days, seemed cold and emotionless. But she did. And despite the bets that the three men had made, (Y/n) had stuck around for longer than any of them had thought. She had remained with Sherlock until she could take no more.

The doctor had heard (Y/n) tell Sherlock that she loved him at least a thousand times. He had seen her make him eat, sleep. And all Sherlock had done was huff and complain in reply. All he had done was treat her poorly. Yet deep down, John knew that his friend did love her. That he had changed so much since she had come into his life. That he was calmer. More in control. More human. And there had even been less body parts in the fridge. It was just that the great Sherlock Holmes had no idea about how to tell (Y/n) how he felt. He could deduce anyone and anything. But he could not see how his emotional constipation had affected (Y/n). He couldn't see that despite the fact that she had done nothing but raise him up and love him, he had only brought her down. John as well as Mary, Greg and Mycroft, noticing how she had transformed from a bright and happy woman, into a shadow. John had even come home a few times to find (Y/n) sat in his front room, sobbing into Mary's arms. Mary only able to shake her head, as he had looked at her. The nurse later telling him that she wasn't sure how much longer (Y/n) could be denied the love that she needed. That she had even told (Y/n) that perhaps, despite the fact that she loved Sherlock, he might just not be the one for her. That she could do with some time away. And then one day (Y/n) did go. She had just up and left. Leaving only a note for Sherlock. A note that the doctor was sure that the detective hadn't even noticed. John reading the tear soaked page. Reading the raw emotions that (Y/n) had finally allowed to spill out. How she would always love Sherlock. That she would never want anyone else. But now, it was obvious that Sherlock could never love her in return. Would never even notice her. And thought more of his microscope than he did of her. But from what John had seen tonight, it was now obvious that Sherlock had read the note. And that (Y/n) leaving had had more of an affect on the consulting detective than he or anyone else would have thought.

John had made two frantic calls, as he had flushed the drug down the toilet. As he had broken the paraphernalia. The first to Greg, so that he could get to Barker Street, and watch over Sherlock. The second to his wife. John well aware that Mary had been the only one that (Y/n) had trusted with her whereabouts. And as soon as soon as the Detective Inspector had stepped foot into the flat, John had set off into the evening. Racing to find the only person that he knew could step Sherlock from spiralling out of control.

John stopped as he got to the large front door, doing his best to catch his breath before he knocked. He didn't know what kind of reception he would get. What he was going to say. But he knew that no matter what, (Y/n) would help. That even though she had left Sherlock, as soon as she knew what had happened, she would be back at Baker Street.

"John? Are you alright? What.........what's going on? Its Sherlock, isn't it?" (Y/n) asked, as she opened the door. Her eyes falling on the sweaty and out of breath doctor. The look of concern in his eyes, telling her more than words ever could.

"Yeah. He.......he's in a bad way, (Y/n). He............." John began. Dropping his head as he thought about how to tell her the next part.

"He........there were drugs in the flat." The doctor finally confessed. John looking up, as he heard (Y/n) gasp. Her body falling against the door.

"Is he................."

"No. He's alive. He just............I know what he did (Y/n). How he made you feel. But he needs you. I know that even though he can't say it, he does love you. You are the only one that can stop him, (Y/n). The only one that he will listen to. He won't do it for me. He won't do it for himself. But I know that he will do it for you. I can't lose him, (Y/n). And I know that you can't, either." John explained. A sense of relief flowing over him, as (Y/n) grabbed for her coat and keys. As she grabbed John's hand and raced out into the street. Hailing a cab and pushing the doctor inside, as she gave the cabbie the address. Offering to pay the man more, if he could get them to Baker Street, quickly.