One thing I love about this show is the way it remains true to the original stories and characters. In that vein, this story contains paraphrased dialogue from Sir Arthur Conan Doyle's book "The Sign of Four". The lifted dialogue is in italics.

OOO

He leaned over his microscope, trying to ignore the maelstrom of chaotic activity going on around him. His flatmate had clearly lost all sense of reason. John Watson had arrived home early from the clinic and had immediately begun rushing about without paying any attention to Sherlock whatsoever. And now, he was singing in the shower. Singing!

Sherlock had never heard John sing before. Why should he sing? Of what use was it? On the contrary, the cacophony was so distracting that Sherlock was entirely unable to concentrate on his work. How could John possibly be thinking about anything at all with such noise going on? Clearly, he was not. Sherlock shuddered at the idea of non-thought.

Heedlessly, John charged out of the bathroom and up the stairs to his room wrapped only in a towel. Sherlock sighed. Was this the action of a combat-trained army officer? Careless! Now there was the unmistakable sound of objects being dropped and/or knocked onto the floor in John's room. Normally, John's movements were precise and fairly graceful, but lately he had grown clumsy, as if he were not really paying proper attention to what he was doing. Could John continue to help Sherlock in The Work if he was going to make a habit of this thoughtless, preoccupied behaviour?

A musky scent preceded John down the stairs. Cologne? John knew better than to clog up Sherlock's sensitive nose with such superfluous olfactory information. A detective needed his senses clear—sight, sound, touch, AND smell. What was John thinking? Sherlock dredged up a half-deleted comment John had made that morning as he left for work. Hmm. Oh, right. John had planned a special evening with Mary tonight.

Mary WAS the problem, wasn't she? John had been fairly normal before he'd met Mary, and then after he started seeing her seriously he'd begun exhibiting this extraordinary behaviour. It was disturbing. John's priorities had gone askew. The Work was apparently fallen to second on John's list.

"How do I look?" John's voice sounded nervous. John was never nervous. More evidence that he was simply not himself anymore.

"She's seen you before, John," Sherlock informed him helpfully, not deigning to look up from his microscope. "Do you really think a singular instance of extravagant personal grooming will make her more likely to accept your proposal?" Surely logic would calm John's absurd case of nerves.

John chuckled. "I suppose not. But could you at least tell me if my tie's on straight?"

Long-suffering Sherlock dragged his attention from his work and looked at John, who was resplendent in his best suit and tie; hair perfect; shoes, still in hand, highly polished. How did John look? "Your heart rate is too high. So is your respiratory rate. Your neck and back muscles are tense, pulling the scar tissue in your shoulder and causing a mild ache, although it's not painful enough for you to have considered taking a pain reliever for it. And your tie is three point five millimetres from centre."

John adjusted his tie. "I should know better than to ask you how I look. You see everything and observe nothing of importance," he grinned mischievously. Sitting down, he proceeded to put on his shoes.

Sherlock felt he must do something to save his friend—his only friend—from further disintegration from a once highly-intelligent and useful assistant to a sentimental puddle of goo. It was too bad, really. Sherlock had actually found Mary Morstan to be a perfectly charming young woman. It was obviously John's own fault, not Mary's, for allowing himself to come apart like this as a result of his feelings for her. Perhaps it was not too late.

"I have to tell you, John, that I cannot congratulate you on your decision," Sherlock began.

John's cheerful face fell, and he sat holding one shoe in his hand. "What do you mean? You can't say you dislike Mary. I know you approve of her. You two were thick as thieves, dissecting that cadaver together last week."

"I have nothing against Mary at all," Sherlock assured him. "In fact, she could be very useful in The Work, with a decided genius of her own. No, it's you who are the problem. You're . . . distracted. Preoccupied."

John smiled. "I expect I am," he admitted, returning to the task of putting his shoe on.

"Love is an emotional thing, and whatever is emotional is opposed to that true cold reason which I place above all things. I could never marry, myself, for fear I might bias my judgment," Sherlock continued.

"Oh, god, I can only imagine!" John exclaimed fervently and chuckled. "Look, I know I've been off my game recently, but I trust my judgment will survive this ordeal. Once our plans have been sorted out, I imagine I'll feel less jittery, and then I'll get back to being 'useful' again."

"You're determined to entangle yourself emotionally, then? Well, so be it. I'll just have to reconcile myself to it," Sherlock sighed magnanimously.

John laughed again. "Yes, you will, thank you very much! Assuming she'll have me, we'll be married very soon, I hope. I know it doesn't look it now, but really, Sherlock, she makes me better. Because love is NOT just an emotional thing. It's a positive action."

"We could have been attacked several times over while you were in the shower, and you'd never have heard it coming over the infernal noise you were making!" Sherlock pointed out.

But John, distractedly emotional John, was too far gone to take such things seriously. He just snorted, amused. "If ninja assassins start climbing in through the windows, I promise to stop singing immediately." Then he sobered, seeing his friend's concern. "Look, Sherlock, I see what you're saying. We do dangerous work, and I've been kidnapped and almost killed frequently enough to know that you're right; we need to be careful. But I can't live my life in fear. I've found a good thing. I only hope she thinks so, too. Try to wish me luck tonight, will you?"

Sherlock gave an almost motionless nod and watched John snatch up his keys and wallet from the coffee table. "Look, I've got tomorrow off and so does Mary. Don't expect me home until day after. And if you text me for any reason that isn't utterly dire, I'll turn off my phone. Understand?"

Turn off his phone! John's mental state was clearly highly compromised, to even consider such an action. "Define dire," he demanded.

"Let me put it this way: if you aren't texting from your death bed, you soon will be," John grinned fondly. "See you later." And he was gone.

Sherlock listened to John's footsteps going down the stairs. Clearly Mrs. Hudson had been listening, too, for she opened her door and accosted him on his way out.

"Don't you look wonderful! So handsome!" she exclaimed. "Here, just let me. . . ." the sound of fingers brushing cloth indicated a fussy brushing off of lint. "There, now you're perfect. I'm so happy for you, dear."

"Thank you, Mrs. Hudson. Wait, are you crying?" John asked, concerning filling his voice.

"Oh, I'm just being a silly old woman. Don't mind me. I'm just so pleased for you. Mary is a lovely girl. And she's a very lucky one, too," Mrs. Hudson sniffed.

John left, and Sherlock spent a few minutes deducing whether that last sound he'd heard was Mrs. Hudson kissing John's cheek or John kissing Mrs. Hudson's. His reverie was interrupted by Mrs. Hudson herself, climbing up the stairs laden with her old, red tea tray.

"Isn't it exciting?" she asked breathlessly, setting the tray down in front of Sherlock. "I love weddings! They make such a lovely couple, too."

"Your own marriage was a disaster, Mrs. Hudson. How could you wish your friend to be afflicted with one?" Sherlock said dismally. Mrs. Hudson swatted him on the arm.

"Stop that! I made a mistake. I married too quickly, and didn't choose carefully. You know perfectly well that John would never do the awful things my husband did. And Mary will never hurt John, you can see it in her face. They'll be lovely together."

Sherlock sipped his tea, but he didn't enjoy it. He was meant to protect John. "Friends protect people." Isn't that what John always said? But how did one protect a friend from himself? And yet, clearly John would be devastated if Mary should refuse him. How did one protect a friend from heartbreak? Sherlock was torn between wishing John luck as he had requested and wishing the entire situation would just go away.

"They'll have such pretty babies, too," Mrs. Hudson prattled on. Sherlock was horrified. This was a development he'd not considered.

"Surely not," he murmured.

Mrs. Hudson didn't hear. "Of course, they'll all be blondes, won't they? With John so blond, and Mary even blonder. And blue eyes, all around. What a picture they'll make, walking down the street together. I always wanted children, myself."

Sherlock shuddered. He was glad when Mrs. Hudson went back downstairs and he could immerse himself in his work once again. He worked until he could hardly hold his eyes open, and then he flopped face-down onto the sofa and dropped into a nightmare-ridden sleep filled with blond, blue-eyed babies crawling heedlessly all over the flat.

OOO

The squeaky seventh step jerked him awake. He didn't move, listening carefully. It was not John's step. Not heavy enough. Not Mrs. Hudson's arthritic tread. Not stealthy, though. Whoever the intruder was, he or she did not mind being heard. The door opened. Sherlock lifted his nose out of the sofa cushion far enough to get a whiff of the intruder's scent without being seen to be awake. Surely that was Mary. But why?

Swiftly, the thoughts flew through Sherlock's mind. John and Mary were meant to spend the day together, to celebrate their engagement. They both had today off work. Perhaps Mary had turned John down. Why should she wish to be married, after all? She had a good life for herself. But no, she was a caring person, and she and John were, at the very least, good friends. A friend would not be happy about hurting her friend's feelings, and she was . . . humming? No, singing, (more singing!) softly, under her breath. A cheerful song, too, not a dirge. So, she and John were now affianced. But where was John? He had been too excited about his plans for this day to have abandoned them easily. Was he on call at the clinic? That must be it—he was called in to work. Sherlock surprised himself by feeling sorry for what must have been a great disappointment for his friend.

But all that did not explain why Mary was in HIS flat and not her own. Singing. And, apparently, rattling pots and pans. Sherlock could not remember John ever making such a din when he was working in the kitchen. He heard the refrigerator door open, and then Mary giggled. John never giggled when he looked into the refrigerator. John sighed. A lot. Sometimes he yelled, but most of the time, he just sighed. Sherlock ran through the catalogue of items he knew were currently in the fridge. Top shelf: four human brains, lined up neatly according to age, youngest to oldest. Second shelf: quart of milk; bowl of apples; jar of index fingers; five heads of cabbage, for practice with his sword. Bottom shelf: sliced cheese, carton of eggs, left-over beans still in the saucepan; tray containing a dissected tongue. Nothing to giggle about, there. But Sherlock had to admit that giggling was an improved response over the uninhibited shrieking of a former lady friend of John's, who had gone looking for cream and found a creamer full of clotting blood instead. Inappropriate reaction versus over-reaction. Mary wins this one.

Mary was, in fact, vastly superior to most of the humans Sherlock had to deal with. She paid attention to him, for one thing. She knew how to listen. She didn't frighten easily, either. And most of the time, she was not an idiot. Sherlock decided to stop pretending to sleep and go see what she wanted.

She turned to smile at him as he walked into the kitchen. "Good morning, Sunshine," she greeted him cheerfully.

"What are you doing?" Sherlock asked impatiently. He disliked cheerfulness in the morning.

"I'm cooking your breakfast," Mary returned brightly.

Long-suffering Sherlock sighed. "I don't eat breakfast."

"Then I'm cooking my own breakfast. You may sit at the table watch me eat it if you like."

He knew he shouldn't be encouraging such outrageously unreasonable behaviour, but he sat at the table anyway. "I see congratulations are in order," he intoned dismally.

She ignored his tone and waved her hand at him, showing off the engagement ring. "Isn't it lovely? It was John's grandmother's. I love antique jewellery," she said, in a perfectly normal voice as if the world hadn't just completely changed. Sherlock remained resolutely silent.

"John was called in this morning. Someone on shift got sick and had to go home, and it was John's turn to fill in," she continued, as if she thought Sherlock might not have worked all this out himself within the first few seconds of her arrival. Insulting! However. . . .

"This doesn't make you angry?" he asked, curious. Many of John's former lady friends had argued with him over his work hours, as if he could actually do anything about it.

"Why should it? He's a doctor. So am I. Doctors keep odd hours. Next time, it might be my turn to spoil our day off by having to go in to work. It's all part of the job." Mary set a plate in front of Sherlock and one for herself on the table then poured them each a cup of tea. Sherlock had not had an omelette in years. John was a good cook, but he couldn't make an omelette to save his life. It smelled delicious. Sherlock frowned.

"We talked all night last night," Mary informed him. "We made a lot of plans. I have money of my own, you know, and with that and my job, and John's pension, we should be able to get by just fine if John quits his job at the clinic and starts working full time with you."

Sherlock stared at her in surprise. He had not expected this at all. In his experience, lovers tended to be selfish, demanding all their needs be met by their mates. Here was Mary, generously offering to give John this gift of freedom to pursue the job he loved by freeing him from one he only tolerated.

"This is something you'd be willing to do?" he asked.

Mary nodded. "I enjoy working at the clinic. It won't be a hardship for me at all. But John feels like he's wasting his time there. And I agree with him—I've seen you two work together, and you do things that no one else can do. It's important work, and if I can do my part to help by making it possible for John to work with you full time, then it's the least I can do."

Sherlock tried a bite of his omelette. It tasted as good as it smelled.

"Tell me about what you were working on last night," Mary encouraged him, and he began to describe his experiments in great detail. Mary's eyes, he noticed, did not glaze over; nor did she twitch or shift about impatiently as so many people did. She even asked clarifying questions and occasionally made an intelligent comment as well. When he had finished talking, he noticed that he had also finished his breakfast, and felt pleasantly filled and warm.

Mary began to clear up, and Sherlock sat back and watched her wash the dishes. He was perceiving things in a new way. Perhaps he was not losing a Watson, but gaining one instead. He could have a full-time Watson at his disposal, with one to spare when she wasn't working at the clinic. Statistically, he could accomplish so much more with even one extra, part-time Watson.

This was going to be interesting.