In theory, he was perfectly able to perform the two tasks at once, which was why his phone was next to his right elbow on the sofa, but he hadn't checked it in nearly an hour. Tiredness played a small part in it, but the main culprit was right there in the crook of his left arm, her tiny but satisfyingly solid form sprawled across his chest. It was impossible for his attention to be anywhere else, really.

Sherlock Holmes was besotted. Completely smitten.

Over the past nine months he had refused to admit even to himself (and let alone to Molly) how much he wanted a daughter, but he would be sure to tell that to Beatrice Holmes once she was old enough to understand. He had known full well it was their last roll of the dice (at nearly forty-three, Molly had made it clear to him that the factory was now shutting down production), and Sherlock felt fortunate to have got lucky in this final play.

Their little girl was smaller than her brothers had been on arrival, but to Sherlock she seemed perfectly proportioned and already had a quietly determined air about her. And she did look like Molly, no doubt about it, with a covering of hazel hair and eyes so dark that Sherlock was convinced they would stay that way (although at only a week old, he knew it was technically too early to tell). The resemblance was something that Sherlock felt probably pleased him even more than it did his wife.

Bea shifted in her sleep, legs suddenly stretching in the hand-me-down onesie that was far too big for her (she would grow into them, Molly said – it wasn't as though she had to carry out any complicated tasks on her own). Sherlock adjusted his hold on his daughter, immediately wincing and having to clamp down on a yelp.

His leg still felt as though it had been stabbed.

Which made sense, seeing as eight days earlier, he had in fact been stabbed.

The whole episode had been infuriating, and also slightly mortifying. When the assailant had come at him and John in the function room of the Finnish embassy, it had seemed tiresomely easy; not only did Sherlock swiftly relieve the man of his machete, but he also quickly took possession of the hunting knife concealed in the thug's ankle holster. Unfortunately, he had not anticipated the small blade hidden inside the attacker's shoe – which was very suddenly not in his shoe, and then almost as suddenly plunged into Sherlock's thigh. As his gaze had moved back and forth between his attacker and his maimed leg, there had been a brief oh, you've got to be kidding me? moment before the reality of the pain set in and he'd fallen sideways into a catering trolley.

Yet another decent scarf ruined by its use as a makeshift tourniquet ("Buy cheaper scarves – or, you know, don't get stabbed," had been John's unhelpful input, as he aggressively ruined the cashmere garment). And this was before a scissor-happy paramedic had insisted on cutting his trouser leg off him, leaving him with a strange half-trouser, half-shorts combination.

Molly, however, had been far less concerned about the losses to his wardrobe. When she'd arrived in his hospital room, and once she had satisfied herself that he wasn't dying, she promptly burst into tears. It was at that point that the shame and remorse had kicked in – up until that point he was still running on adrenaline, and annoyed at himself for failing to foresee the third knife, but Molly soon made him forget all of that. Flooded with pregnancy hormones, she couldn't seem to decide whether she was furious with him or relieved that he was okay (the kissing/shouting combination had been very confusing, particularly in his weakened state).

Anyway, Molly was still blaming this incident for the fact that, less than two hours later, she was in labour. Luckily, they hadn't actually left the hospital, and there followed a ridiculous scene where they both had to be transported by wheelchair from the Minor Injuries Unit (minor injuries!) to the Maternity ward, Sherlock still wearing his ruined trousers and towing a saline drip.

Sherlock acknowledged that he hadn't exactly been the best possible birth companion, confined as he was to a chair for most of Molly's labour. He had tried not to think too much about the searing pain in his leg as one of the midwives handed him a glass of water and another couple of paracetamols – it was probably considered a Bit Not Good to request a second supply of Entonox (diamorphine was a no-no for obvious reasons). But Molly needed him, and he was there, and after (mercifully) only a couple more hours, so was their daughter. And when Molly reached for him and they shared an exhausted kiss, Sherlock understood that he was forgiven – there was no time to dwell, they had bigger things to deal with.

As he lay stretched out on the sofa now, he could almost feel himself dozing off when he heard the soft padding of feet on the wood floor.

"Is everything alright, Rosie?" he asked, glancing over his shoulder.

His goddaughter nodded, and as she came over, Sherlock carefully eased himself and Bea into a sitting position. Bea uttered a noise that sounded somewhat like a seabird in distress, which made Rosie giggle.

"Does your leg still hurt, Uncle Sherlock?" she whispered, with an expression of concern.

"I'm fine, thank you," he told her.

Molly had insisted on giving the children a watered-down version of the facts, telling them all that Sherlock had 'fallen on something sharp while trying to catch a bad person'. He went along with it, even though it somewhat down-played his brilliance, and made the incident sound more slapstick-comedy-sketch than life-or-death-combat.

"Can I look at her if I'm quiet?" Rosie asked, leaning in slightly.

"I wouldn't be too concerned about that, Rosie," he replied. "Her brothers aren't exactly excelling in that department."

William and Teddy had so far shown only intermittent interest in their sister. William had been suspicious from the outset, as Bea's unexpectedly early arrival meant that she failed to bring him a present as Teddy had done, and his general opinion since then seemed to be that the new baby was 'boring'. Sherlock understood that completely – it was hard to deny that new babies were fundamentally extremely boring, although if they were your own, he had learned, they were also, paradoxically, completely captivating at the same time.

Teddy's response had been to regress to infant mode himself, and he had to be repeatedly hauled out of Bea's Moses basket or her car seat. Either that, or he tried to elbow his way onto Molly's lap every time his sister required sustenance. Lestrade had reported that Teddy had even offered him his sister in exchange for a ride in a police car.

On this particular day, both boys were out with Sherlock's parents, who on this visit had managed to combine their twin passions of visiting their grandchildren and berating their younger son for his thoughtlessness. As though to spite him, they had taken William and Teddy to some appalling-sounding children's theatre production – although for the price of three hours of relative quiet, his parents could have taken his sons to a public hanging for all Sherlock cared.

"I'm pleased you and Aunty Molly decided to have a girl this time," Rosie announced, nudging her bottom onto a small gap on the sofa.

"That's not quite how it works," Sherlock replied. "It's just random; nobody decides. We didn't actually know that Bea was a girl until she was born."

Rosie considered this for a moment.

"Oh. Well, then it was really unfair that William and Teddy were both boys. What if you hadn't had another baby, and you'd just had two boys?"

Sherlock gave a sniff of laughter, although it was clear that Rosie was deadly serious.

"We'd have still had you," he pointed out.

She wrinkled her nose, giving Sherlock a smile that suggested he was being weird, but she was going to allow it; it was one step away from rolling her eyes at him – just give her a couple of years.

"Uncle Sherlock?" Rosie continued after a moment, resting her elbows on her knees as she collected her thoughts.

"Hm?"

"How do babies get born?"

Sherlock blinked, gently cleared his throat, then blinked again. His goddaughter was watching him with a very expectant look. Generally speaking, he felt it was ridiculous and unnecessary to sugarcoat things for children - in his experience, children tended to understand and accept things far better than adults - but this was new territory for him.

"Well, it depends," he said, stalling. "For instance, William was born via a process called a Caesarean section. It's an operation wherein a surgeon uses a knife to-"

"A knife?"

Rosie looked horrified, and he hadn't even got to the description of how the knife was used. In hindsight, probably not the best way to approach the subject.

"Did the surgeon cut Aunty Molly open and take William out?"

Sherlock frowned, tilting his head to one side.

"That was broadly what happened, yes," he confirmed, hurriedly adding, "Though it was perfectly fine and Aunty Molly wasn't in any pain."

Unlike my recent knife-related encounter, he thought, allowing himself a moment of self-pity.

Now it was Rosie's turn to frown.

"But...okay. Were you there, Uncle Sherlock? Did you see the knife?"

Again, Sherlock wasn't in the habit of lying to the children in his care.

"I was there, yes - I was able to watch it happening on a screen, so that I didn't get in the way of the doctors."

At this, Rosie's look of horror returned, as though he was some terrible, depraved monster who derived thrills from watching his wife be savagely cut into by a group of strangers.

"It's fine," he heard himself saying again. "And actually, most babies - you, Teddy and Bea for instance - arrive via a different method, without knives."

Oh, now he'd done it. If ever there was a leading statement, that was it; now he was going to have to swiftly think of an age-appropriate way of describing the process of childbirth that both closed the subject to his satisfaction, but also ensured that Rosie didn't suffer long-term mental trauma that would render her unable to contemplate bearing her own children.

But instead...

"So...how did Bea get inside Aunty Molly's tummy in the first place?"

Wow - that was…actually even worse. This would be the perfect moment for his week-old daughter to erupt into a hungry rage, thus derailing the whole course of the conversation, but naturally Bea refused to oblige him.

"Ah, yes," Sherlock began, stalling. "I, ah...has your daddy talked to you about any of this before, Rosie?"

For God's sake, John was a doctor - that was the least he could do. And if Sherlock found out that John had put him up to this in some way, he was going to have to hack his Tinder account again (the last time he had merely made an accurate amendment to his friend's height, but that was barely scratching the surface of the damage he could do).

"No, but Daddy only has me, and you've had three babies – well, Aunty Molly has - so I thought you'd definitely know," came the somewhat-logical response.

Somewhere out there, Sherlock could picture Mary hooting with laughter at his discomfort, saying Go on then, what are you waiting for? Once again, he thought about how lightly he had accepted the offered role of godfather - cake at the after-do, occasionally turn up for the celebration of milestones, guide Rosie step by step through the periodic table. This was not supposed to be his area.

He gave Bea a surreptitious little jolt, in case that would do the trick, but she didn't stir.

"Well, Rosie," he began, clearing his throat again. "Grown-ups, adults...they sometimes like each other so much that they...they want to give each other a...a special cuddle. And sometimes, as a result of that, a baby is, erm, made."

Immediately, he cringed at his use of the phrase 'special cuddle'. He was now no better than his own parents, who had merrily misled him for years over correct anatomical terminology (boarding school had proven a rude awakening).

It seemed to have got Rosie thinking, though; she nodded slowly, her brow furrowed in the exact same way that John's did when he was trying to follow Sherlock's line of thinking.

"So, you gave Aunty Molly a special cuddle to show how much you love her?"

At this moment, if someone had wanted to stab Sherlock in the other leg, he honestly wouldn't have minded.

"Yes, I do – I mean, I did," Sherlock confirmed. "It's sort of a mutual thing. Aunty Molly is fairly keen on giving me special cuddles, too."

"And that made a baby?"

"Yes."

Rosie bit the edge of her lip into her mouth while she mulled this over for a moment. Sherlock felt himself almost holding his breath, glancing at the clock above the fireplace. Molly did say an hour's nap, and technically an hour was up, so would it be completely unforgiveable to send Rosie up to wake her?

"So, Uncle Sherlock - is a special cuddle the same as sex?"

Sherlock's head snapped up from where his gaze had been resting on Bea's head.

"Sorry, what?"

Rosie patiently repeated her question, adding, "Because Aunty Molly told me about that."

He felt his mouth fall open in a dumb display of confusion.

"When did Aunty Molly tell you about, ah, tell you about…that?" he asked, gingerly picking his way over the words.

Rosie shrugged, as though time was a mere social construct that made very little impact on her life.

"Not long ago. Before Bea was born," she replied. "I asked her how come William and Teddy look like you but came out of her tummy. So she explained."

It was hard to know what to say to this, but one very definite question sprung to mind, and it tumbled out of his mouth in a very undignified splutter.

"Rosie, if Aunty Molly explained it all to you, then why are you asking me?"

"Because it sounded so weird," she replied, wrinkling her nose again in mild distaste. "I needed some corrugated evidence."

"Corroborating evidence?" Sherlock queried. He couldn't help but feel he knew where this quest for investigative rigour had come from, and it would be nothing but hypocrisy to be critical of Rosie's approach.

She nodded vigorously.

"I understand completely," he told her, shifting Bea a little higher onto his shoulder. "Because you're right, it is weird. But then most of what human beings do makes little sense. Anyway, you don't need to concern yourself with any of it for a long time yet - it was certainly a while before I gave it much serious consideration."

"Yes, I know," Rosie replied plainly. "Aunty Molly said that, too."

Sherlock felt a muscle in his neck twitch.

"Oh, she did, did she?"

It was heartening to know that his wife felt able to discuss his sexual history with their seven-year-old goddaughter; perhaps she could have seen fit to fill him in on their entire discourse before he found himself in this awkward conversational cul-de-sac. Anyway, he liked to think that during the last few years he'd gone some way towards making up for lost time.

"Is it okay if I have a drink?" Rosie asked, performing an abrupt change of subject.

A finger of whisky sounded like a remarkably good idea, but Sherlock suspected this wasn't what Rosie had in mind. He told her to help herself, watching as she propelled herself from the sofa, planted a quick sisterly kiss on Bea's head, and scuttered off towards the living room door. Sherlock wondered exactly when his goddaughter had sprouted those long limbs, and whether Molly had noticed too. It seemed improbable that one day, the helpless little parcel currently spread-eagled against his chest would be the same.

Sherlock glanced down at the product of his and Molly's 'special cuddling' habit.

"I hope you were paying attention there, Beatrice," he murmured against the soft fuzz covering the crown of her head. "Because you and I won't be broaching that subject again for at least twenty-five years, by which time, of course, you will be a brilliant and celebrated criminologist or research chemist."

He could hear the clink of a glass on the kitchen table, the sound of the fridge door being closed.

"Although," Sherlock continued, finger ghosting over the shell of his daughter's ear. "If you have any questions in the intervening years, no matter how embarrassing they may seem, I recommend you have a word with your Uncle John."