Molly was in the middle of cleaning the bathroom sink when she heard her phone buzz on the table out on the landing. She tilted her wrist to check her watch – it was too late in the day for it to be Mike, asking her to come in and cover a shift. And anyway, if it was, she was going to ignore it; she had covered more than her fair share of sickness and family emergencies, and it was a beautiful August morning, and as soon as she finished the bathroom, she was going to take a book into the garden and enjoy it.

The phone buzzed again.

She only knew one person who was that insistent. And he knew she wasn't at work, because Molly knew for a fact that he memorised her shifts - so if he wanted lab access or body parts today, he was going to have to try to unburn some of those bridges he'd spectacularly torched with her colleagues at Bart's.

She was reaching up to scrub the shower screen when another text arrived.

Sighing, she peeled off one of her pink rubber gloves and picked up her phone.

Are you at home? – SH

Followed almost immediately by…

Do you have plans? – SH

Molly rolled her eyes. Would it make the slightest bit of difference if she did? She immediately wondered where this was going; was he going to demand her presence at Baker Street, for assistance with an experiment? He'd been doing that a lot recently, particularly since Rosie's christening. The last time had been a bit weird; Molly knew for a fact that he had conducted the very same experiment a few weeks earlier, and anyway, he hadn't seemed to care particularly about the results. When the takeaway – which Molly hadn't even realised he'd ordered - arrived, he forgot about science completely.

She would never in a million years say it to him – and he would sooner set fire to his violin than admit it - but it struck her that perhaps Sherlock Holmes was lonely.

Molly, are you actually awake? – SH

She sighed, smiling slightly at the question. The idea that she might be asleep at eleven o'clock on a Friday morning was laughable.

Yes - I'm cleaning – MH

There was a short pause.

Why? – SH

She rolled her eyes again.

Because the cleaning fairies are so busy at Baker Street that they can't make it this week – MH

Molly pushed a few strands of loose hair off her forehead, and tightened her hair in its no-nonsense-domestic-chores ponytail. Time enough for a response to come through.

It looks clean enough to me – SH

A frown of confusion was just starting to form on her face when the penny dropped. Somewhere, within a few metres of her house, Sherlock Holmes was enjoying being a smartarse. She could just picture the look of self-satisfaction on that annoyingly handsome face.

Molly padded down the stairs barefoot, and swung open the front door, speech already prepared.

"So, what is-" – she stopped. "Oh."

"Good morning, Molly," Sherlock replied, with a small, neat smile.

This was…not what she was expecting. There was something wrong with this picture.

Sherlock Holmes was wearing a baby carrier.

"Sorry, didn't I mention Rosie was with me?" he asked, with casual innocence. "Say hello, Rosie. Don't mind your Aunt Molly – she'll catch up in a minute."

Rosie, facing Sherlock's chest in the carrier and wearing a yellow sunhat, twisted her head to try to see her godmother. Flicking Sherlock a look of suspicion, Molly took a step down from the front door to greet Rosie, lifting the hat to place a kiss on her forehead, and taking her tiny hand in hers.

"Are John and Mary alright?" she asked, cautiously.

Sherlock's brow furrowed.

"Yes. Why wouldn't they be?"

Molly jammed her hands into the pockets of her shorts, suddenly felt slightly guilty about the train of thought that led her to ask the question.

"No, no reason, I…"

"Isn't this what godparents do?" Sherlock queried, waving his hands above Rosie.

"Yeah, I suppose," Molly acknowledged, unable to shake that flicker of scepticism. "So...you're babysitting?"

"Indeed," he replied, with a tight smile. "Providing John and Mary with a much-needed opportunity for rest and relaxation, while also allowing them to rediscover themselves as a couple, independent of their roles as parents."

Molly folded her arms; that sounded suspiciously like something that might have been gleaned from a book or website.

"I see."

"The speed at which John propelled Rosie and me towards the front door, and the less-than-subtle wink he gave me on departure, suggested he believes that they're going to have sex - but I strongly suspect that what they will actually be doing is sleeping."

Molly gave a brief snort of laughter. Now that was out of the way, she could then address the other very strange element of this tableau.

"W-what are you wearing?" she queried.

Sherlock looked down at his attire, and then back up at her, as though he didn't understand the question.

"You're, um, wearing jeans," she elaborated.

"Yeeess."

"I didn't know you owned any, that's all," Molly said, thinking it probably wasn't worth mentioning the casual short-sleeved shirt, or the sunglasses perched atop his curls. And she definitely wasn't mentioning the effect the whole ensemble was having on her.

"I didn't know you owned denim cut-offs," Sherlock countered. "We're both full of surprises, apparently."

Molly felt a blush rise in her cheeks, despite herself. Suddenly, her legs felt very exposed indeed; she found herself feeling immensely relieved that she'd at least shaved them the night before - before harshly reprimanding herself for thinking that way.

"It's summer and I'm cleaning," she replied, defensively. "And anyway, I wasn't expecting company, remember?"

Sherlock looked down at her from underneath raised eyebrows.

"You should probably change," he told her, stepping past her into the hallway. "Not dramatically – but perhaps something with slightly fewer holes."

Oh god – he'd noticed the holes in her vest top. Of course he had. Again, it wasn't as though anyone dressed up to do housework, which Sherlock would know if he ever actually did any. He gave a small shooing gesture in the direction of her stairs – the git.

"You could wear that nice t-shirt," Sherlock suggested. "The-"

He waved his hand vaguely, searching for the word.

"-the nautical one."

Molly frowned, eventually realising that he was probably talking about a top she owned that had little ships and anchors printed all over it. She wasn't sure how she should take it that a) apparently Sherlock noticed what she wore, and b) he apparently liked something that she wore. She was already making for the stairs when she stopped herself.

"Hang on, why am I changing?" she asked, already hating herself a little bit for her instinct to comply with his wishes.

Sherlock's face spread into a smile.

"We're taking Rosie out, of course."

Molly folded her arms again, stepping away from the stairs.

"You offered to babysit," she reminded him. "I have other plans for my day off."

"Nnnnooo, you don't," he replied. "Therefore, I naturally assumed that you would jump at the opportunity to spend time with your brilliant and accomplished goddaughter."

Molly's gaze moved between the little girl who had captured her heart on arrival in the world five months ago, and the man who had dramatically abducted it so long ago it didn't bear thinking about. She didn't know which of them was harder to refuse. But it was a beautiful day outside, and she knew she would immediately feel like the world's worst godmother if she dug her heels in just to prove some kind of point to Sherlock (or rather to herself about Sherlock).

She took Rosie's hand again, wiggling her little fingers and provoking a delighted shriek. When she glanced up at Sherlock, he was looking down at her with pursed lips, one eyebrow slightly raised; he knew that he'd got his way.

"Give me five minutes," Molly told him. "But if it turns out that all this is because you want to avoid changing nappies, you're on your own."

00000000

It wasn't about the nappies – that much eventually became clear as the morning wore on. Molly's suspicions were first raised when Sherlock hailed a cab and told the driver to take them to Holland Park, all the way over the other side of central London. It was in the taxi that she also noticed his footwear – instead of his usual, highly-polished dress shoes, Sherlock was wearing a pair of trainers. They looked expensive - and box-fresh. In fact, she realised, everything he was wearing looked brand new.

"Why are we going to Holland Park?" she queried.

"It's nice there," he replied. "I thought we could take Rosie to the park; babies like fresh air –that's a thing, apparently."

"Okay, but there's a park half a mile from my house," she pointed out. "And also a pretty huge one down the road from your flat."

He wouldn't say anything further on the matter, and Molly continued her hopeless battle of not being horribly distracted by the spectacle of Sherlock with a baby in his arms.

The cab deposited them in an area that was completely unknown to Molly, with wide, tree-lined roads and the ludicrous 'lifestyle' boutiques where people pay thirty quid for a bunch of twigs. Sherlock apparently seemed certain of their destination and, shouldering Rosie's changing bag, she followed him in the direction of a gated park in the middle of a square. Grand Georgian townhouses flanked the park on three sides, with black front doors that gleamed in the sunshine like patent leather, and frankly ridiculous cars parked outside.

"Reach into my pocket," Sherlock said, as they were standing outside the gate.

"W-what?" Molly replied, certain she must have misheard.

He gave a small sigh.

"My trouser pocket - I can't reach it because of this baby…contraption," he explained. "I need to get something out of it."

"Shall I just take Rosie out of the carrier?" Molly offered. It seemed altogether less likely to end in some kind of hideous embarrassment.

"Honestly, Molly, it's really a very simple request," Sherlock said, hitching Rosie up slightly so that she could get better access to his left hip pocket. "If it makes any difference, there's a key in there."

"Oh," she replied, swallowing. "Okay."

Vowing to get this over with as quickly as possible, she slid her fingers into the pocket in question; thankfully, she didn't have to delve far before they made contact with said key. Sherlock seemed to flinch slightly at the contact, and as she gingerly withdrew her hand, Molly tried to ignore the warmth that had transferred from Sherlock's thigh to the key – and, briefly, to her own fingertips.

"That's, ah…" Sherlock said, as she handed him the key. "Thank you."

For the briefest of moments, he looked slightly glazed.

Quickly recovering, he fitted the key to the lock in the gate and pushed it open, gesturing for Molly to go in front of him. Once they were both safely in the park, he swiftly locked the gate behind him.

"Can't afford to let any old riff-raff in," he said, with a smile.

Molly stared at him, as he and Rosie moved past her on the path.

"Sherlock, don't you have to be a resident here to have a key?"

She was absolutely certain that in her jeans and cheery t-shirt, she was not going to pass for the wife of a Russian oligarch, or a minor member of the Saudi royal family.

"Nope," he replied, waiting for her to catch up. "You just have to have a key. Where you acquire that key…well, that's another matter."

The small, private park was beautiful, with well-tended rose bushes and flower beds, and a spotless play area with a sandpit. They were not alone, and briefly attracted the attention of a small group of women – immaculately coiffed and manicured – who were sitting on some benches beside their designer prams. To Molly's surprise, Sherlock gave them a small, cheerful wave before taking her hand and leading her to a bench of their own. There, he unclipped the harness of the baby carrier, lifted Rosie out and sat her on his knee, murmuring to her as he adjusted her sunhat.

Rosie looked so delighted to be free that Molly shook off that slight feeling of unreality and remembered why she wanted to come on this outing in the first place. She took Rosie across to the swings, securing her goddaughter on her knee and giving her a gentle swing; although Sherlock had pulled his sunglasses down over his eyes, she could tell his gaze was moving between her and the other users of the park. Eventually, she returned to the bench, intending to give Rosie some milk, but when she stopped digging around in the changing bag and shuffled back on the seat, she felt her back come into contact with something. It turned out to be Sherlock's arm – and he made no attempt to move it.

This was all becoming a little too uncanny.

"I…I brought some snacks," she said, deciding that the best approach to the wandering arm was to ignore it. "If you'll hold her for a sec, I'll get them out."

Sherlock quickly shook his head.

"Thank you," he replied, distractedly. "Not eating today."

And that was where her confirmation came from.

Immediately, Molly's mind flashed back several years to the canteen at Bart's, standing in the queue and deliberating over the pasta and the pork. Digestion slows me down. Yes, it was unscientific bollocks, but she knew what it meant.

"You're working," Molly said, forcing herself to look at him.

Sherlock flipped up his sunglasses momentarily, long enough to look at her sideways. Molly didn't know what she was expecting, but there was no obvious sign of guilt or remorse in his expression.

"Yes, of course I'm working," he replied, slowly. "Why else would I be risking the possibility of Rosie socialising with the offspring of such odious human beings?"

Molly sighed.

"So the jeans, the brand-new trainers, all of…this," she said, wearily. "You're essentially undercover right now?"

"Essentially," he nodded. "As are you."

Molly snorted.

"Um, no, I'm not," she replied. "As far as I'm concerned, I'm here to spend time with Rosie and enjoy the sunshine."

"Yes. And you're doing both of those things. But for the purpose of the conversation that is about to take place, you're also something else."

There was no time to quiz him any further, because when Molly looked up, she saw that one of the women from the other bench was approaching. She was in languorous pursuit of a toddler with a mop of blond hair and a designer t-shirt that must have cost more than Molly's entire outfit.

"I'm so sorry about Hugo," the woman drawled, not sounding in the least bit sorry, as the little boy grabbed hold of the bench. "He always gets very excited when he sees new people here."

"Not at all," Sherlock replied.

His breezy tone was surprise enough, but Molly had barely got over that when she felt Sherlock's hand come to rest on her shoulder, his thumb lazily stroking her clavicle through her t-shirt. Oh, she was going to get him for this later.

"Your little girl is adorable," the woman continued with the least convincing smile Molly had ever seen, even taking into constraints of Botox. "What's her name?"

Molly opened her mouth, but Sherlock beat her to it.

"Allegra," he replied, without pause.

Allegra?

With her milk-stained M&S romper suit, Rosie Watson was hardly a very convincing Allegra.

"Oh, that's darling," the woman replied. "And I think my little boy might be right – I don't think we have seen you in here before…?"

As though from a script, Sherlock began to spin a story about them being new to the neighbourhood, renting while they got a feel for the area.

"It's time we put down roots, isn't it, darling?" he added. "But that's easier said than done with my fiancée's line of work; she's in fashion, so you understand how it is."

He moved his arm from her shoulder so that he could take her hand instead.

Molly's jaw tightened; the only upside to this situation would be the look on Sherlock's face when she told him that he was never, ever, not-in-a-million-years, getting further access to body parts from the morgue.

"Oh?" the woman replied. "Really?"

She was looking Molly up and down with an expression that was definitely dubious. Molly managed a small nod, hating herself for playing along.

"Several of my friends are in the industry," she continued. "Which fashion house do you work for?"

"I…"

"She's more of a consultant," Sherlock cut in. "Anyway, she jets all over the world so much, it's a wonder that we managed to get this one in the oven – isn't that right, darling?"

He gave a very un-Sherlock-like chuckle, and Molly couldn't resist giving his thumb a sharp pinch – although it seemed to do nothing to put him off his stride.

"So, anyway, I'm doing the whole parental leave thing, and I'm absolutely loving it," he continued. "Completely besotted, having the time of my life. In fact, I'm trying to persuade her that we need to get started on another one fairly soon."

Molly felt her face explode in a horrifyingly warm blush, and Rosie's bottle nearly slipped from her hand.

"Well, it's a fantastic area," the woman said with a shrug. "Great restaurants, lots of little one-off boutiques - and the competition for prep-schools is reassuringly savage."

"What about nurseries?" Sherlock asked. "We'll need to start looking around for Allegra."

Molly cringed at the repetition of Rosie's ridiculous undercover pseudonym.

"Very long waiting lists for the best day nurseries," the woman replied, picking an invisible fleck of something from her son's hair. "But, of course, there are a number of ways to jump the queue – I'm sure you understand."

Sherlock gave a conspiratorial chuckle.

"Naturally," he replied, smiling.

Still holding Molly's hand, he dug into Rosie's baby carrier and produced a pen and paper.

"I, ah, I don't suppose you could write down a few names for me?" he asked. "The nurseries you'd recommend, obviously, but any names it would be…useful for us to know. If it isn't too much trouble?"

The woman looked uncertain for a moment, but eventually took the paper and pen from Sherlock's hand, returning it to him thirty seconds later with some scribbled notes. Sherlock thanked her with an ingratiating smile, folding and pocketing the note.

"You'll have to excuse me," she said. "I have to get Hugo to our hot yoga class."

As soon as the coast was clear, Molly watched as Sherlock dug out his phone and flicked to the photo gallery, pulling up and zooming in on an image of an envelope.

"Same handwriting," he said, a smile spreading across his face. "Almost too easy."

Molly sighed.

"You, um, you can let go of my hand now."

"Hm?" Sherlock replied, releasing her hand, but keeping his eyes on his phone. "Oh. Yes. Sorry about that. Over-improvised in the moment without fully thinking through the consequences – just seemed…more appropriate."

"'Over-improvised'?" she queried, replacing the top on Rosie's bottle and shifting her goddaughter onto her shoulder.

"No engagement ring," he muttered.

She didn't know what to say to that, but was getting the distinct feeling that if she wanted to salvage any of her day off – not to mention her pride – it was time to take decisive action. Giving Rosie a kiss, she got to her feet and placed the little girl on Sherlock's lap. Immediately, he looked up at her, questioningly.

"She'll need to be changed pretty soon, and make sure you keep her sunhat on," Molly told him, setting off in the direction of the gate before he was able to reply.

Within seconds, Sherlock had caught up to her, Rosie in one arm and the changing bag and carrier tangled around the other. The whole scene would have been slightly comic if she wasn't so bloody exasperated with him.

"Molly?"

When she turned to face him, there was a moment when he looked genuinely confused.

"Don't worry, Sherlock, I'm not going to blow your cover," she sighed.

He arched an eyebrow.

"Blow my what?"

Molly fired him a look – he was picking now, this moment, to flirt with her?

"In case you haven't already deduced it, I'm going home, Sherlock," she told him. "I'm glad you got what you needed, I hope it was for a good cause, but – and I can't believe I actually have to say this – I really have no interest in being your beard again in the future."

She set off again, but Sherlock caught her arm. Rosie started to whimper, probably sensing the disquiet between her godparents, and Molly couldn't help but feel a pang of guilt, despite herself.

"It was for a good cause," Sherlock replied. "I've been following a trail on and off for weeks, and today has provided me with a key piece of the puzzle."

"Fine. But why did you have to involve me? Why couldn't you…I don't know, just be a dad doing the childcare? That is a thing that some men do. Or if you really, genuinely needed my help, why didn't you just ask? I might actually have said yes. But I'm tired of being lied to, Sherlock, and I don't like you using Rosie as some kind of bait."

She watched the expression on his face change; saw him swallow, blink. One of his hands had seemed to automatically start rubbing soothing circles on Rosie's back.

He cleared his throat.

"Molly, you are not my 'beard', or stooge, or whatever other insulting thing you might think," he began slowly. "I wanted you to come with me as my partner."

Molly rolled her eyes.

"Partnership implies equality, Sherlock," she sighed. "Not one person playing the other one for an idiot."

"That's not what I was doing!" he said, an undercurrent of hurt in his voice that he definitely hadn't earned. "I…I wanted you to come with me today because…because, with you, I am believable as an ordinary man."

"Oh," Molly replied. "Thanks a bunch."

He shook his head, annoyed more with himself than with her.

"No, I mean it as a compliment," he continued quickly. "You're the only person I know who can do that, Molly. And also…I have it on good authority that we are convincing. That this -" – he waved his hand between the two of them – "is convincing."

Molly blinked at him, her mouth suddenly feeling dry.

"Who-? What good authority?"

Sherlock cleared his throat.

"Well, for a start, there were the seven people at Rosie's christening who assumed you were my wife – eight if you include the vicar," he replied. "Although I suspect he was touting for further business."

"For a start?" Molly prompted, her voice suddenly coming out higher than expected.

"Yes," he replied, pulling his lips together.

Molly narrowed her eyes at him.

"There were others?"

"Possibly."

"Who?"

Sherlock sighed.

"Really, Molly, why on earth does that matter? The weight of evidence-"

"Sherlock, if you don't tell me, I'm going to take out my phone right now and tell Mary the real reason why you were so keen to babysit today," she told him.

Sherlock licked his lips, stalling.

"If I tell you, will you stay?"

Molly folded her arms across her chest.

"If you tell me and you can guarantee that Rosie isn't going to be in any danger...then I'll think about it."

Sherlock cleared his throat, his gaze flicking to a point somewhere above her head.

"In which case, were you to take out your phone and call the aforementioned person, then…you may not be entirely on the wrong track."

Molly took in this information.

Mary. Mary had said it. Immediately, Molly found her mind surging with questions about the exact words their friend had used, the context of those words, and what she even meant by saying them in the first place.

But she knew that Sherlock would never supply this information, and her sense of self-preservation was too strong to seek it from Mary. Instead, she would fold up that information - like Sherlock with his handwriting sample - tuck it away, and revisit it on those occasions when she really needed it. It was silly, but sometimes she just needed something small like that.

"Okay," she said finally, nodding. "I'll stay and help you. But one more condition."

Sherlock raised his eyebrows, waiting for it.

"I get to pick my undercover name," she told him, feeling the beginnings of a ridiculous grin starting to form.

"Fine."

"And..."

"And?!" he asked, incredulously.

"I get to pick yours too."

Sherlock narrowed his eyes at her, as though considering whether this was now more trouble than it was worth. But Molly could see he was acquiescing.

They made their way to the park gate, and Molly stopped.

"Just out of interest, Molly," Sherlock began. "What were you going to do when you reached the gate and remembered it was locked? Tunnel under the hedge using your Oyster card? Ask one of those women for a boost over the railings?"

He seemed to be recovering some of his swagger, which, considering he was supposed to be in mild disgrace, was unacceptable to Molly.

"Then?" she mused, doing her best to withhold a grin. "Then I would definitely have had to blow your cover, Sherlock. As publicly as possible."

A quick, darting look at Sherlock at that moment made the whole fiasco worthwhile – the tips of his ears were a delightful shade of pink, and Molly was fairly sure she was getting her first direct experience of what John called Sherlock's 'buffering' mode. Well, well.

"Come on, Rosie," Molly said, taking the baby out of Sherlock's arms. "I think your Uncle Sherlock might need a minute. Then we'll go and make him buy us some lunch."

THE END