Cake
Sherlock smelled something burning. Hmmm… not gasoline, in fact nothing explosive. So not his problem.
He was bored. He hadn't had a case in weeks, and John was off somewhere being married. Hadn't he come by recently? Sherlock couldn't keep his days straight. It was coming from the kitchen.
The kitchen… There was something important about the kitchen. Must not have been important, otherwise he would have remembered. Oh well. Time for a cigarette, maybe.
Yes, he was smoking again, for the therapeutic effect, of course. They used to help him concentrate. Not so much now. Now they were a distraction, took his mind off of the nothing that continued to happen every day since…
Don't think about it. Don't think about John. You know what happens if you do.
That was certainly true. John was the only thing that kept him clean, and without him, Sherlock had fallen apart completely. Thinking of John only brought back memories of the old days, before Sarah took him away; it brought endless regrets to an otherwise fine day of coping. Reminded Sherlock of his bad new habits. He could not stop replaying the day of the fake drug bust. I'm clean, he had protested. But God knew that was far from true these days.
He heard someone in the kitchen. A shout. John. Oh, right. He had been back recently. He was leaving tomorrow. Or something.
"No!" John shouted. Either that, or "know!" Statistically, the first one was more likely, but you could never tell with homophones. They were confusing. And vital, like that one time in Bulgaria, when-
"Shit!" No doubt what that meant. As to why it had been shouted, even Sherlock couldn't guess. Sherlock pondered this for a moment. He seemed to remember something about a cake, but he couldn't trust his memory much these days…
"Sherlock…" Drawn out, frustration, a complaint.
OH! THAT cake! He remembered quite clearly now. John had put it in before work, told Sherlock to check it in an hour. But he had spent his afternoon investigating the freezing point of arsenic-spiked champagne. Then he had given in and polished off the bottle of champagne. Then another one. After that, nothing. He was completely out of it.
"Coming, John!" he yelled. And together they cleaned the oven of burned cake. John made a new one.
This happened with a different food every couple of weeks, so John wasn't frustrated as much as amazed at Sherlock's lack of attention for things that didn't interest him. He also enjoyed the feeling of putting those three words together, though he could never explain why.
Once everything was cleaned up, and the new cake in the oven, Sherlock and John retired to the living room, where they took some time to catch up. They hadn't seen each other much for over a month, and there was plenty to tell. And, despite Sherlock's best efforts that afternoon, there was a bottle of champagne to ease the conversation.
At the end of an hour, Sherlock felt like his old self again. He was happy, he was talking to a real person, and John was back…
"… For good?" he inquired hopefully.
John started to speak. Stopped. Cleared his throat. Looked away.
"Sarah's pregnant," he finally said, and left without looking back.