He hadn't lied when he'd said girlfriends weren't his area. When he ultimately reversed his stance on that topic, Sherlock therefore decided to really research how it ought to be done. After all, there's no point in doing anything unless you're going to be the best at it, boyfriending (ugh) included.
There was a lot of literature on the subject but it was written for (and about) idiots. Conducting the experiments himself, which would normally be the appropriate course of action in such a situation, was unviable. Successful psychosocial experimentation mostly required a control group… and when he considered what might happen if he were an unsatisfactory romantic partner he suffered from chilled extremities and an unpleasant sensation of heaviness just below the sternum.
The solution came to him, as it often did, in the company of John. For someone of only adequate intelligence, the doctor was unbeatable as a promoter of thought.
"John," Sherlock said, "You're very short and angry, and yet Mary seems quite happy with you. How did you manage that?"
Watson inhaled slowly through his nose, and replied levelly, "I am one inch shorter than the average British man-"
"Mmm, try three."
"No. And oddly enough most of the time when I'm angry you're in the same room and talking. It's not that much of a stretch that I could make Mary happy. What's wrong with me?"
"The list is on my laptop, I'll email it to you when I get home. Clearly you've learnt the trick since my departure. You never managed to keep a woman for more than two months before."
John snorted, retrieved his coffee cup from the dashboard of the battered Ford Fiesta, and took a sip. "That's down to you, mate."
"What?"
"I'd dated Mary for nine months before you came back and she had to deal with you. She'd already gotten attached to me by that point."
"Sunk costs are a legitimate element of behavioral economics, but-"
"Look, this isn't about me and Mary. This is about you and Molly. And so I'm going to tell you the truth and that is that there's no trick to it. All you do in a relationship is to try not to be a complete arsehole all the time – in your case this might involve occasionally thinking things you don't say – and she tries to do the same and it sometimes works out."
"It never worked out for you before."
"Because that's the point of dating. You have to see if your particular set of horrible personality flaws mesh with her set of horrible personality flaws. It's always going to fail, until it succeeds. Oh. Oh, hey, we've got a lookie-loo at ten o'clock."
Sherlock looked to the left, and saw a jittery teenager scanning the car-park. "Right," he said, "Let's catch a crocodile-smuggler."
The Lab Notebook of Sherlock Holmes
Hypothesis: Mary is happy with John because he has a higher income than she does and is thus able to provide her with a superior standard of living. Financial insecurity is often a motive for offing one's husband; financial security, therefore, must be a desirable attribute for a man to have.
Method: Apply scrutiny to Watson finances
Result: John provides approx. 2/3 of Watson family monetary support (point in favour). John could double current contribution should he be inclined to focus his energies on medicine rather than the pursuit of criminals (point against). Mary does not appear to be upset by this failure and actively encourages him to take cases with me (point against). Mary herself could produce 2x her current income by spending 1-2 months per annum engaged in professional espionage as repeatedly offered by Mycroft Holmes (point against). Also according to M.H., American security agencies pay much more to their off-the-books representatives than their UK counterparts, and so resuming her prior employment would enable a significant increase in income even over that (point against)
Conclusion: Mary's personal contentment does not involve money, at least not above the level of middle-class.
Notes: Damn, this would have been a good one. A few more dull but lucrative "help me prove infidelity and invalidate my prenuptial agreement" cases would have easily let me surpass Molly's income, and I have half a dozen of them in my deleted emails folder at this moment.
Hypothesis: Mary is happy with John because John donated the genetic material to produce a viable and appealing offspring.
Method: Observe similar parental relationships among Londoners of their class and age.
Result: The Watsons have a child (Melita) who is unusually charming compared to other children of her age and background. This child demonstrates no particular traits that are especially characteristic of John apart from blonde hair and blue eyes, both of which are also present in Mary. As these traits are recessive, Mary had motivation to choose a mate with John's phenotype in order to produce them (point in favour).
Other women appear to be equally attached to obviously inferior children (point against). Sentiment and biological imperative, once again, defeat reason.
Conclusion: Indeterminate. Mary might have been equally happy with some other sprog by some other father.
Notes: This one is a possibility and to the best of my knowledge I could probably provide Molly with an acceptable child should she want one. Mem: Find out the salient characteristics of a semen analysis and perform one next time you have the opportunity, as unqualified assumptions can lead to error. Does Molly actually want a child? She seems to like them but has never bought up the topic despite her advancing age, and she's very rigorous about contraception. Is fatherhood actually something I could do, given that even the idea that I might have a child with Molly triggered my first bona fide panic attack in twenty years? Why does this have to be so complicated?
Sherlock slammed the notebook closed and drummed his fingers on the table in irritation.
As a general rule he preferred having a narrow set of acquaintances, since it minimized the number of tedious social gatherings he was required to attend. But on occasions like this, where advice might have come in handy, it was frustrating to find out that all the people you knew were incompetent morons who couldn't manage a successful romantic relationship without the aid of horse tranquilizers and bribery. Even the Watsons had spent six of the first seven months of their marriage actively contemplating divorce.
Oddly enough, under other circumstances, Molly would have been the best one to approach for an answer to this. She'd had a respectable dating life and had been the one to end all of her relationships, so presumably she knew what she was doing. But she had terrible skills in selecting a satisfactory partner, and he did not want to draw her attention to that fact, since he himself was no exception to the general rule.
He narrowed it down to men (since he himself was one) and members of long-term relationships (since that was the goal). And then he began his inquiries.
Mike Stamford
Mike Stamford, upon being asked "how do you make a woman happy with you" had replied, "The last thing I did that made her happy was getting a vasectomy. Get a vasectomy. Everyone should."
Upon more in-depth examination, Stamford's wife was both unusually fecund and unusually prone to multiple births. Thus they had produced a set of twins and a set of triplets in the space of two years, and had five children in diapers at the time Sherlock inquired of him. While this justified Stamford's haunted eyes and three-stone weight loss, it hardly seemed applicable to his own particular situation. Oddly, despite his panic attack at the thought of potential fatherhood, the hypothetical elimination of the chance made him feel… sad? Possibly?
Something to examine later.
George Lestrade
Lestrade sighed and lit another Silk Cut when he was asked about keeping a woman happy.
"You can't take them for granted, Sherlock," he said, drawing in smoke. "If you do, there's always someone out there who won't. You have to let them know that you value them or they'll just… slip away."
This seemed like valid advice from a man whose twenty-year marriage had been ended by adultery, and so the next time he saw Molly, he said, "You are the most skillful pathologist I've ever encountered and your work is extremely useful."
At that point they were surrounded by MI-5 agents, so Molly just smiled and continued her description of the corpse and the manner of death.
But it seemed to work, so he set up a randomizer app on his phone to remind him to remind her of her own merits.
Father
Siger Holmes must have had some useful knowledge about women, given that he had managed to live with Sherlock's mother (who was one) for almost fifty years without either of them becoming what most people would consider insane. Sherlock had meant to ask him, he truly had. He'd taken the old man to the British Museum and bought him a sandwich in the café, and Siger had even said, "Is everything going well with your young lady?" which was an ideal opening…
And then he had a legitimate flashback of himself aged thirteen, spotty and agitated, being sat down in Siger's tobacco-fugged study for "the talk".
He just couldn't face another iteration of that excruciating event. Being beaten with a pipe in a Serbian prison had nothing on being obliged to hear his father talk about sex, love, and relationships. Sherlock had simply replied, "Very well," and they'd gone for a look at the Mildenhall treasure.
Philip Anderson
Asking Anderson was an act of sheer desperation. But the man had managed to pull Sally Donovan while still married to someone else and looking like a water rat, so he presumably had some sort of insight.
Anderson flushed, pleasedly, and it occurred to Sherlock that he'd never previously asked for or wanted the man's opinion about any subject.
"I suppose," he said, after some consideration, "That what they really want is for you to respect them. To know that you think of them as a person and an equal instead of some sort of… lifestyle accessory, I guess?"
Sherlock stared at him in dismay. Yes, obviously sexism was a legitimate problem and given her race and career choice Donovan was subject to more than her fair share of it. Anderson probably had a point there. It was just that his point was utterly pointless in his own situation. Despite what everyone believed, Sherlock Holmes was well aware of his numerous and fascinating issues, but casual misogyny was not one of them. Instead, his misogyny, misandry, and general misanthropy were always intentional and purposeful. Women en masse were at least as intelligent as men (so not very), their malignities equally explainable and generally far more justified.
If anything, he was Molly's lifestyle accessory, not the other way 'round. She was far nearer to being a functional human being than he was.
Two bloody weeks he'd been at this and he'd learnt nothing that would be of any real use to him in keeping Molly happy. He was absolutely and completely fucked.