Sherlock was sitting on the couch, glaring at his hands in front of him. He was bored. Lestrade didn't have any interesting cases; it was all just boring procedures. No one had contacted him for help. Even John was disappointing this evening; he'd taken Sarah out for the evening. Sherlock scowled at the memory; John was clearly thinking about having a good time with her instead of staying here and entertaining him.
When he heard the outside door open and close, Sherlock sat up a little straighter. John was home; they could talk and the boredom would go away at least for a little while. Then Sherlock heard the second set of footsteps. No pleasant conversation, then; at best, he'd have to listen to the two of them being a couple.
Instead of coming in, though, John just poked his head into the lounge. "We're going straight up, Sherlock; it's been a long day. Have a good night." He paused, waiting for Sherlock's response.
Sherlock waved a hand at him, trying to convey that he couldn't be interrupted from thinking great thoughts. He listened to the couple walk upstairs and close the bedroom door. To prevent himself from listening for what he knew was about to happen, he applied his mind to this new problem.
Until now, Sarah had only been a minor problem. True, their dates did result in John's being inaccessible, until something went wrong and Sherlock needed to come to the rescue. However, until now, even when John spent the night at her place, he slept on the lilo. Now, John was enough of a traditionalist that, if they'd become physical, he would be thinking long-term. It wasn't an immediate danger, but sometime in the next year or so Sherlock stood to lose the only flatmate he'd ever been able to keep. John would marry, move away, begin a family and Sherlock would become his eccentric friend that he saw when there was time. He wouldn't even get weekends and alternate Tuesdays!
The most obvious solution, of course, was to drive Sarah off. It wouldn't be that difficult. All Sherlock would have to do would be to contact John with important cases at inconvenient times. They'd have to be important; that would be the trickiest part. John would get increasingly annoyed if the interruptions were for trivial matters.
He picked up the violin and began tuning it while he thought. No, driving Sarah off was only a short-term solution. Once she was gone, John would simply find someone else. He was reasonably good-looking, above average in intelligence, and far above average in kindness. No, keeping John unattached was a short-term solution at best and, if he realized what Sherlock was doing, he might leave even sooner.
Of course, if Sherlock had any interest whatsoever, he could probably seduce John into a relationship. He was already meeting John's need to be needed, for adventure, for companionship. John thought of himself as totally heterosexual, an opinion of which Sherlock had seen no reason to disabuse him, but it meant that Sherlock would actually have to be interested in a sexual relationship with John to be successful. Although they were being as discrete as possible in a flat, Sherlock could hear the bed creaking in an unmistakable rhythm. He scowled. That was as bad as John leaving.
About to start making the violin screech as unpleasantly as possible, Sherlock stopped. He preferred having John living here at Baker Street. His life was much more pleasant and comfortable with John in it. But was where John lived really the most important part? Thinking about it, Sherlock realized that he'd been assuming for some time that John would eventually marry and move; that wasn't what twisted his stomach. It was the thought that John would leave, that Sherlock would only see him on rare occasions, that he found so upsetting.
Given the assumption that John would eventually marry and move out, what Sherlock needed to do was to find a woman who was willing to share John with him. She could have him for sleeping and sex, for all the dreary, boring, things John liked so much; Sherlock could have him when he needed someone to talk with, someone to make those obvious, wrong, but so inspiring comments. John would get sex, danger and companionship from more than one person, which most people seemed to think preferable than having only one friend.
Now that he had a plan, Sherlock moved on to the second part. He needed to find a woman that met all of John's needs while leaving him available for Sherlock. And, there, Sarah might do admirably. She did complain about Sherlock's monopolising of John's time, but that was probably because she thought she was losing to Sherlock. The first step, then, would be to get Sarah on-side.
The creaking upstairs had stopped, but Sherlock could still hear the murmur of voices upstairs. Placing his violin under his chin, he began playing, starting with Mendelssohn and quickly losing himself to the music. When he looked up again, it had been over two hours and upstairs was quiet.
Sherlock was dressed when John and Sarah came down the next morning. Something wasn't quite right. "It's a bit late for you, isn't it?" he asked. They hadn't been that late the night before.
"The clinic's been mad all week," John said, stretching a little. "We were both ready to fall over by the time the film was over."
"Was that you playing last night?" Sarah asked, smiling as John turned the kettle on. "It was lovely."
"He must be trying to get on your good side," John said, grinning. "I only get music about half the time, and Mycroft only gets screeching."
"It's all he deserves," Sherlock said, staring at the wall. He looked up at Sarah. "So, you liked it?"
"Very much," she said. With a non-grudging smile, she was much prettier than Sherlock remembered.
John, on the other hand, looked worried. "What's wrong?"
"Why should anything be wrong?" Sherlock asked.
"You're being nice," John said. "It's unnerving. What do you want?"
"Nothing," Sherlock said, looking innocent. John didn't look convinced.
"Honestly, John," Sarah said, laughing. "If you treated me like this when I'm being nice, I'd never be nice to you again."
"Can't have that," John said, smiling at her. "How does a picnic sound?"
Sherlock started to answer when he realised that John was asking Sarah. Reminding himself of his plan from last night, he didn't say anything.
"Sounds good to me," Sarah said. "How about you, Sherlock?"
"What?" Sherlock looked over at her, startled. That wasn't in the plan.
"Do you have a case?" John asked. When Sherlock shook his head, John smiled. "Then you should come with us. It's a beautiful day; you can get fresh air and sunshine without any blood. You can tell us everyone's life story if you get too bored."
Sherlock smiled. Perfect. He had John to entertain him and John would be in an even better mood with Sarah along.
Opening the refrigerator, Sarah stared at the head. Then she shut the refrigerator. "We'll need to stop to pick up our lunch," she said, shaking her head. "I'm not eating anything out of that refrigerator."
Oh, well, Sherlock thought. At least she hadn't screamed.