When the day came to go to John and Mary's house, Sherlock spent the entire morning working himself up to it. He changed clothes about six different times, let three cups of tea go cold because he was thinking too much and forgot about them, and ignored the bell ringing for nearly a whole minute before he finally heard it.

It was Lestrade, asking for help on a case. Sherlock agreed to go but said he had to be back in good time. He even went with Lestrade in his police car, just to save time.

When he finally reached the house he actually felt excited. He had worked through every scenario in his head, from not knowing what to talk about to feeling like he was intruding to not liking the food, before coming here and now he felt confident he would actually be able to enjoy himself.

But after only a few minutes he realised that those weren't the sorts of things he should have been worrying about. He looked around the house and saw John's possessions scattered all over, mixed in with Mary's, and surrounded by new items that clearly belonged to both. Sherlock could remember where each and every single one of John's things had been at Baker Street, and the hole they had left behind.

At dinner he had to keep himself from fidgeting. He kept tapping his foot and fingering melodies on his thigh to try to calm himself down. Everywhere he looked he saw the life that John had been building without him and he suddenly felt out of place.

John and Mary had clearly done their best to make Sherlock feel comfortable. Dinner had been one of his favourite dishes, and if Sherlock didn't say much no one forced him to talk. Instead John and Mary kept the conversation going by themselves until the detective joined in. But even so Sherlock still felt like a third wheel.

The couple already had their own inside jokes and domestic habits. Not that it was surprising; they had been living together for some time now. But while he was happy that John had found someone, it hurt him to see the life that he was missing out on. Regardless of what he may have said he always enjoyed living with John, and not just because he did the shopping and cooking. It felt good to have someone around, even if they weren't always doing things together. It felt even better to have someone to worry about him and remind him to take care of his transport. There were times when he genuinely forgot because he was too busy with a case and John was always there to remind him.

After a tour of the house, dinner and two games of Cluedo Sherlock couldn't take it anymore so he made an excuse to leave. He told John that he had to go home and start an experiment to help Lestrade on a case. It wasn't even a complete lie; Lestrade did need his help, but all Sherlock needed at the moment was to look through all the evidence.

When he left the house he couldn't bring himself to go back to Baker Street. The only thing that would accomplish would be to remind him of how alone he left. It didn't matter that John had told him that he would always be there for him and that nothing and no one were going to replace him. Sherlock believed that, he really did, but that didn't change the fact that he felt like he was taking up space in John's life. Space that John could fill with bigger and better things.

He wandered the streets of London until morning when he went to visit Lestrade to work on the case. He kept this up for days, only returning to Baker Street to shower and change clothes; otherwise he was either at Scotland Yard, the crime scene or at Bart's conducting his investigation. Most of the time he worked through the night so that neither Molly nor Lestrade saw that he wasn't doing much of anything else. Occasionally he would collapse on the sofa and fall asleep for a few hours but as soon as he woke up he went right back to work. He had to keep his mind occupied and the work had always been one of two ways.

But eventually the work ran out. No matter how big Lestrade's caseload was, it wasn't infinite, and there were many cases he could solve without Sherlock's help. At this point Sherlock had no choice but to go back to the flat. But as soon as he walked in he was met, once again, with the painful sight of John's empty chair.

He stripped off his coat, throwing it on the sofa carelessly, rolled up his sleeves and made his way over to the chair. It took a while but eventually he was able to drag it all the way up to the room upstairs- John's old room, his brain supplied uselessly. When he was done he sat in his own chair and simply stared. All he could see was the kitchen. There were no more morose empty chairs to upset him, and he thought he'd solved his problem. But unfortunately John's presence lingered all over the flat.

As he looked at the kitchen all Sherlock could think about were all the times they had poured over cases on the table and all the take away they had eaten there because they were too tired to make dinner for themselves. John was everywhere he looked, and yet he was nowhere.

After that he avoided Baker Street as much as he could. He started spending his afternoons with Mrs Hudson. He helped her with the shopping and even had some cooking lessons from her. After that he spent some time at Angelo's under the pretence of surveillance for a case, but that only lasted a few days.

When Lestrade text him about a case he jumped at the chance for something to do. But it was boring and easy and took barely any time to solve. He was desperate for something to keep his mind occupied; the alternative to the work was starting to sound very appealing.

It was three days after that Sherlock met Wiggins through his homeless network. After days and days of trying desperately to keep his mind occupied and utterly failing it didn't take long for Sherlock to give in to his habit again. With no one nagging, worrying or watching him, Sherlock felt free to do whatever he wanted. And what he wanted was to get high.

He started spending most of his time in an endless cycle of getting high and coming down and getting high again. He ignored every text and call on his mobile, trying to tell himself that it wasn't John's name on his screen. He would have continued that way if one day he hadn't had to return to Baker Street to get more money and scared Mrs Hudson half to death with his appearance. When she asked he told her it was for a case. When she asked why John had come over looking for him Sherlock told her that the case was too dangerous for John so he hadn't told him.

Sherlock felt bad about lying to Mrs Hudson but he didn't have to worry for long when he stumbled across Charles Augustus Magnussen. He now had a distraction as well as what he felt was a genuine excuse for his behaviour. He couldn't just give up the drugs because Magnussen would know he was pretending, and he had to believe Sherlock wasn't a threat- that the drugs were his pressure point.

It wasn't long into his investigation when Sherlock realised that he would need to get close to Janine. He cleaned up and played the part with her when he needed to, and it even served to settle Mrs Hudson's worries when she saw him around Baker Street again.

The investigation was progressing, but slowly. The detective tried not to think about how much quicker it would go if he had John by his side, but he couldn't bring himself to pick up the phone.

He tried to remind himself he didn't believe in coincidences when, one day, John Watson inadvertently came to him. it had been so long since he'd seen or spoken to John that he couldn't keep the smile off his face when he finally saw his friend. It took a while for him to realise where he was, what he looked like, and what was clearly implied in the place John had found him in.

But Sherlock Holmes was, after all, a master in the art of disguise. So he pretended he was okay, pushed away John's and Mycroft's concerns, and kept telling himself that the drugs were the only pressure point he had to worry about.

It wasn't until he saw Mary with a gun pointed at Magnussen's head and felt the tendrils of guilt wrapping themselves around him again that he realised his mistake. He had done what he blamed so many others for; seeing but not observing. And in doing so he had made a very serious mistake.

As the bullet entered and wreaked havoc on his body he had one final thought before the pain took over.

Caring is not an advantage.