Molly shuffled the last of the lunch dishes further along the kitchen counter in the general direction of the dishwasher; it was Will's turn to empty and re-stack it, but that wasn't likely to happen any time soon. From the living room, she could hear a seemingly endless loop of Mozart's Minuet, as her older son – overseen by Sherlock – practiced for his Grade 5 violin exam. Despite his natural talent, Will had a love/hate relationship with the violin, and his lessons with Sherlock had been known to come to an abrupt end with one or both of them flouncing out of the living room – but Molly knew that neither of them would want the lessons to stop.

Interspersed with Mozart-on-repeat were intermittent clattering sounds from the hallway, where Teddy had set up one of his labyrinthine marble-runs on the staircase. What had started as a seventh birthday present from his grandparents had turned into a project now in its third month, with Teddy's piggy bank emptied to provide new ramps and junctions for his creation. The whole thing was undoubtedly a massive trip-hazard (Sherlock cursed it virtually every time he went up or down the stairs), but they were all forbidden to touch it – and when Bea had decided to 'help' the previous week, Teddy had sulked in the treehouse for an hour.

Bea was the only one who was currently in Molly's line of sight; she was sitting in the dog bed, talking very animatedly to their beagle as she attempted to groom him with a doll's hairbrush. Three years on, Molly still wasn't sure why she'd agreed to getting a puppy just weeks after Bea was born, but it did mean that girl and dog were pretty inseparable – Bea, rather than Sherlock, was definitely his master.

At the time, it was agreed that one of the boys could choose the dog and the other one could name it – which was why they ended up with a beagle named Mycroft. William was insistent that the dog looked like their uncle when he was annoyed, and while Sherlock had used every bribe and incentive he could think of to prevent him having to call his brother's name across the park and at crime scenes, Will couldn't be bought. (Although, had Teddy done the naming and Will the choosing, they might be the proud owners of a noble bloodhound called Wrinkle-Face, which even Sherlock had to admit was worse.) Because family get-togethers started to get a little confusing as a result, canine Mycroft tended to be referred to as Mike instead (although Sherlock felt that Human Mycroft was just as likely to eat up dinner scraps as his canine namesake).

"Mummy, we hate that song!" Bea pronounced, frowning at the wall that adjoined the living room. Apparently, she was speaking for the dog, too, who in fairness did look equally put-out.

"I know, sweetheart," Molly replied sympathetically. "But they'll be finished soon, and then you're all going out for a bit, aren't you? To the pirate playground?"

This was the family shorthand for the Diana Memorial Playground, one of the few family-centric attractions in London that Sherlock could just about tolerate – he could even overlook the prevalence of sand, so long as he had a strong cup of coffee in his hand and could connect to a wi-fi hotspot.

"Are you coming, Mummy?" Bea asked, leaning over to rest her cheek on the dog's back.

"I'm going to meet you later. I've got some work to do first, remember?"

"What work?" her daughter asked, suspiciously. All three children were always deeply mistrustful when either of their parents claimed to have something more important to do.

"People have sent lots of things for me to read," Molly explained, dragging her laptop bag onto the dining room table.

"What people?" Bea enquired, with a sceptical frown.

Molly smiled; it clearly sounded to Bea as though this was an attempt on her mother's part to indulge in the highly illegal activity of weekend relaxation.

"People who want to work at the hospital, I suppose. Or another hospital."

In the past few years, Molly had found herself gradually shifting from the day-to-day work in the morgue to more regular hours in the path lab; Mike Stamford (who she usually had to refer to by his full name these days, to avoid further confusion with the dog) had given her additional responsibilities in supervising students on their placements – hence the paperwork - and was encouraging her to finally make the jump from Specialist Registrar to Consultant. She supposed she would probably have done it already if it wasn't for the three small humans and the big lanky one who had gloriously and unexpectedly changed the course of her life.

As Molly started to make a pot of tea to accompany the assignments, she noticed both Bea and the dog cock an ear almost simultaneously. Then the dog let out a single bark.

"Doorbell!" Bea shouted, leaping up and running for the hallway, Mike not far behind her.

An identical cry came from Teddy on the stairs, and at the same time the sound of violin music came to an abrupt halt. Molly's immediate thought was that she had forgotten something because, let's face it, it was surprisingly easy to do these days. She hoped it wasn't another reporter, or a particularly persistent client of Sherlock's who'd discovered his home address (they tended to get very short shrift - partly because Sherlock kept a strict separation of work and home, but also, Molly suspected, because it was hard to maintain a carefully cultivated air of detachment and mystique while surrounded by scooters, Lego and abandoned socks).

"It's Rosie!" Teddy called, as Molly was emerging into the hallway.

They must have arranged something with John and then overlooked it – or maybe John and Rosie were going out with Sherlock and the children, and Sherlock had just forgotten to mention it. Molly was pretty sure that Rosie had swimming lessons on a Saturday afternoon, but maybe they'd come to an end.

It was only once Molly had a clear view of the front door that certain things started to make sense; when she looked beyond her ten-year-old goddaughter, standing there on the step, she realised there was no adult in sight.

"Rosie, where's you dad?" Molly asked, hurrying over, squeezing past the two small onlookers.

In those few seconds, she tried to gather as much data as possible: Rosie looked physically unharmed, she wasn't crying. There was something amiss in what she was wearing, though – namely her brightly-coloured school backpack, and a slightly uncertain expression.

"Um, he's just at home…I think," she replied, hesitantly.

"You think?" Molly said, ushering Rosie into the house and closing the door. "He didn't come with you?"

"Well…no," Rosie said, uneasily. "I kind of came by myself."

"You…by yourself," Molly echoed, feeling her chest tighten. "But how did you get here?"

Rosie shrugged.

"Just the Tube. I've got my Zip Oyster card."

"Cool!" declared Teddy, who was too easily thrilled by deviant behaviour.

"Oh, that's not fair!" came the voice of Will, who Molly wasn't even aware was in the room. "How come Rosie's allowed to go on the Tube by herself and I'm not? She's only a bit older than me."

One of Will's latest obsessions was the London Underground; he was fascinated by the network, the routes and in particular the old, disused (or never used) stations. He kept a record of every station he'd visited - could name each one and give you a selection of statistics on them - and was determined to tick off every single one.

"I'm fairly certain she's not," came Sherlock's reply, as he emerged from the living room.

A quick glance at her husband told Molly that he was as concerned as she was, perhaps more so.

"You've had a disagreement with your dad, and now you want to know whether you can come and live here instead?" Sherlock said, after only a couple of moments.

It was more statement of fact than question, and Molly saw Rosie's expression change; Sherlock was right, and she hated it. It explained the backpack, though.

"Is that it?" Molly prompted gently.

Sherlock still occasionally forgot that sometimes, just sometimes, people liked to have the chance to explain themselves, rather than being deduced (it took a while for him to understand that when his children excitedly said "guess what?", the last thing they wanted him to do was actually guess).

"Can I?" Rosie quickly asked. "I could sleep in with Bea, and I can help you look after her."

"Yes! Yes! Yes!" Bea shrieked, each utterance punctuated by a jump, causing the dog to run in an excited circle. "Come on, Rosie!"

Bea grabbed Rosie's coat-sleeve, trying to drag her towards the stairs, decision clearly made in her mind. Before she could get very far, though, Sherlock had put out his arm to hold them back; Molly could see he was about to say something when his attention was drawn instead to his buzzing phone. He made the briefest of eye-contact with her, enough to confirm her instinct that it was John calling.

"Yes, John, she's here…" Sherlock said, before ducking back into the living room.

The second he'd gone, Rosie thrust her hands into her jeans pockets.

"I'm not talking to him," she said defiantly. "And I'm not going home."

"I ran away, too, you know," Teddy put in, with a nonchalant air.

Molly heard a snort from Will, sounding exactly like his father.

"No, you didn't," he told his brother. "The neighbour's garden doesn't count. And anyway, we could see you from the attic."

Teddy had indeed made a bid for independence a few weeks earlier, but spurred on more by the spirit of exploration than by discontentment with his family. Molly still felt a pang of guilt that she hadn't noticed his absence for half an hour, and could still vividly recall the stab of panic she'd felt when he didn't respond to her calling his name. Eventually, Will had spotted his brother from his favoured bolt-hole at the top of the house, by which time Teddy had managed to make it as far as the neighbour's back garden three doors down, either by scaling fences, finding holes in them, or squeezing through foliage (Molly was still picking dead leaves out of his curls the next morning).

"Mummy!"

"Hm, sorry, what?" Molly replied, distracted as she tried to make out the phone call going on in the next room.

"Is Rosie going to stay?" Bea asked with a note of impatience.

"Well, we're definitely not going to throw her out into the street," Molly told her, catching a tiny smile flicker across Rosie's face before being quickly banished. "But I think Rosie needs to come into the sitting room with me for a few minutes, and the rest of you can start getting ready to go out."

There was a collective whine and some low-level grumbling from the younger members of the Holmes family. Molly felt she was probably only stalling for time; she couldn't see how, in their current uncertain situation, she was going to be sitting down reading assignments anytime soon.

She pointed at each one of them in turn.

"William – violin away, shoes on, find everyone's Oyster cards; Teddy – proper trousers, please, then shoes; and Bea – have a go putting your shoes on, and bring me Mike's lead and your hairbrush."

"No hairbrush!" Bea protested.

Molly sighed; admittedly, it wasn't the time to reopen the campaign to tame her daughter's hair (thank god Bea had inherited her straight hair, at least).

"Everyone, go," Molly said, with a shooing motion. "Rosie will still be here when you come back."

All three of them were too curious to find out what was going on, but eventually they got the message. As they dispersed, Molly noticed Will looking back briefly at Rosie, although Rosie was looking at the hallway floor at that moment. In the past year or so, their older son had started to change; it had taken Molly a while to put her finger on it, but empathy was at the heart of it – William had gained an insight into other people, watched them closely, started to put himself in their shoes. He seemed to reserve a special sort of quiet watchfulness for Rosie, though, and Molly wondered whether he felt protective of her, picking up on the way Sherlock was with her and following his lead.

Molly gave a quick knock at the living room door and opened it, encouraging Rosie in ahead of her. Sherlock was no longer on the phone, instead sitting in his favoured chair, leaning forward with his elbows resting on his knees. Molly assumed that Toby had been chased off the chair, judging by the narrow-eyed stare their aged cat was giving Sherlock from his position on one of the sofa cushions.

She could see by the set of Sherlock's jaw and a quality in his eyes that he had heard something from John that he hadn't been expecting; that this was not just a disagreement over clothes or schoolwork or whether Rosie could have a phone. Molly guided Rosie over to the sofa, taking her hand as they sat down together.

"Your, ah, your dad's calmed down a little," Sherlock said, in a low, gentle tone that made Molly feel another, sudden rush of love for him. "But I think you gave him a fright."

Rosie withdrew her hand from Molly's, shoving it underneath her leg instead.

"I don't care," she replied, tersely. "He deserved it."

Molly saw Sherlock's gaze meet hers for a moment, before he regrouped.

"I know you feel that way, Rosie, but it wasn't right to disappear like that," he continued. "London is a busy city, and not everyone you meet has good intentions."

"I'm not stupid!" Rosie retorted. "I know that! But I've been on the Tube millions of times and I knew the way. I thought you'd be happy to see me."

"We're always happy to see you," Molly put in, chancing the action of resting her hand on Rosie's knee. Rosie stared at it as though it was an unwanted tarantula. "But I know you know this wasn't the right thing to do, whatever happened with your dad."

"You asked him about your mum," Sherlock said, trying to urge her to meet his gaze. "About how she died. Because someone at school asked you."

Molly felt her heart lurch into her throat, but she forced it back down. So many times over the years – since before Rosie could even talk - she and Sherlock had lain in the darkness of their bedroom, talking in whispers about this very thing, this very scenario. There was no reason this should come as a surprise, but the suddenness of it left her feeling completely unprepared.

"He always said she died by accident," Rosie said. "That she wasn't meant to get hurt, but she did anyway."

"That's right," Sherlock replied, swallowing. "Your dad was telling you the truth. What…what was it that he told you today that upset you so much?"

Molly knew exactly what was on his mind at that moment – but that he was ready to face it when it hit.

"I didn't know he was there with her," Rosie replied. "He was right there when she died, that's what he said!"

"Rosie," Sherlock said, his lips pursing for a moment as though knowing he had one chance to get this right. "You know that sometimes in the kind of work we do, your dad and I, we are brought into contact with people who are not very nice, to say the least - people who have done terrible things."

"And you catch them," Rosie nodded. "I know that."

"Yes. Sometimes," Sherlock replied, his measured tone meeting Rosie's slight indignation. "But even when they're caught, some people want to feel as though they've still won; want you to know that you haven't taken away all of their power. Do you understand that?"

Rosie shrugged, and this was enough for her godfather to continue.

"Well, that's what happened that day, with your mum," he said, his voice quavering for a moment. "I was with her. And it's true – Mar-…your mum wasn't supposed to get hurt…I was. The person we'd caught wanted to hurt me, so she could show me that I wasn't as clever as I thought I was."

Molly felt herself aching for both of them all over again, unsure of where to put herself or what to say that could be of any comfort to either.

"It was a lady?" Rosie asked. It was clearly a detail that John had left out of his bare-bones explanation.

"Yes, an older woman, someone who worked quietly in an office for most of her life," Sherlock confirmed. "Bad people come in all shapes and sizes, Rosie. It took me a surprisingly long time to work that out."

"But why didn't my dad do anything!" Rosie hit back, the crux of her anger and pain bursting to get out. "He's a doctor, and he was there, and he didn't do anything to save her."

This time, Molly didn't care if Rosie didn't want it; she put her arm around the little girl's shoulders, her hand clasping the top of her arm. She could feel that Rosie was almost shaking with indignation and the sudden release of adrenaline.

"Your dad got there just after it happened," Sherlock told her, slowly, calmly. "But even if he'd been right there, Rosie, there was nothing he could have done – your mum was too badly hurt."

"But he's saved people before, hasn't he?" Rosie pressed. "My dad. He was a doctor in the army, and people get shot and bombed and everything in the army. And you've told me about other times he's saved people's lives, Uncle Sherlock, when you've been solving stuff together."

Molly could see a flicker of desperation in Sherlock's eyes, as though he didn't know how to add to what he'd already said, that he'd played his hand and now he had nothing.

"It's just unfair, Rosie," Molly said, before she really knew she was going to say it. "It's horribly, horribly unfair, and all of us – everyone – wish things were different, because your mum didn't deserve that, but when she got hurt, it… it was just one of those injuries that takes people away very quickly."

She could feel a familiar thickness rising in the back of her throat, and it made her squeeze Rosie a little tighter – for whose benefit, she wasn't sure.

"And you know what?" Molly continued. "It's fine to be angry, it's normal to be angry, and none of us think that's wrong – but don't be angry at your dad."

Rosie's shoulders heaved once, and Molly felt her shudder.

"He should have looked after her," Rosie said, more quietly now. "Like Uncle Sherlock looks after you."

"Aunty Molly looks after me, too," Sherlock put in. "And your mum looked after your dad. But, Rosie, your dad never stopped doing that, even up to the very last moment. He and your mum both knew that she…that nobody could help her, so your dad did the only thing he could do."

Molly could hear the slight tremble return to Sherlock's voice, and it was obvious to her that he was reliving it. He'd described to her, words spilling like a dam being opened, how he'd stood there in the darkness of the aquarium, almost paralysed by his own powerlessness. How he felt he had no right to witness Mary's last moments, John's last seconds with his wife, particularly given the role he believed he had played. But how he also couldn't turn away – how he didn't deserve to be spared the agony.

Molly knew enough of the events to feel sufficiently confident to take over from Sherlock.

"He was there right until the end, sweetheart," she said in a firm whisper. "He hugged your mum tightly and told her how much he loved her, and – and I know that's what she must have needed right then. It was everything."

Tears stung her own eyes now, as they did whenever Molly allowed herself to imagine what Mary must have felt in those last moments, knowing they were her last, knowing she would never go home. But it was right for Rosie to see this, right that she should understand how much her mother was loved and missed.

Rosie was quiet now, suddenly looking much smaller, her anger apparently draining away to make room for something else. From elsewhere in the house, Molly could hear the thuds and raised voices of her own children in the process of getting ready, and she willed them not to come barrelling into the living room any time soon (tact and timing were skills that certainly neither Teddy nor Bea had yet mastered).

"Do I have to go home now?" Rosie asked, barely looking up.

"Do you want to?" Sherlock asked.

Rosie shrugged, her hand creeping across the sofa cushion to gently stroke Toby's back.

"You dad will probably want to talk to you a bit more," Molly suggested. "But…maybe you could start by speaking to him on the phone?"

She glanced at Sherlock before she spoke again.

"I'll ring him, and we'll both talk to him," Molly continued. "And if he says it's okay, perhaps you could stay here - just for tonight. Although you've got to promise that you'll let your dad pick you up first thing tomorrow and talk to him properly."

Rosie glanced up, suddenly looking as though a cloud had lifted.

"Is that a deal?" Sherlock asked, eyebrow raised.

She nodded.

"Good girl," he smiled. "Now, you and Aunt Molly see to that phone call, and I'll go and see which new parts of the house the other three miscreants have managed to destroy in the past fifteen minutes."

0000000

A little over ten minutes later, things were starting to look somewhat clearer and more hopeful. John, although understandably still recovering from the shock of Rosie's disappearance – and the discovery that his daughter was strong-headed enough to go to those lengths – had calmed down sufficiently to hold a measured conversation with her. He'd confided to Molly that he hadn't for a moment considered what those new details about Mary's death might mean to Rosie, how she would interpret them; Molly just hoped he wouldn't use this as an excuse to reinstate those deep-seated feeling of guilt he'd held for so long.

John had conceded, too, that it might not be a bad idea for Rosie to stay with them for the night – it would give them both a little more time and space to gather their thoughts. As it was just the two of them, Molly knew that John and Rosie had an intense bond that, while by and large was a wonderful thing, also had the potential to make Rosie feel cosseted and claustrophobic, especially while she was still too young to go off and develop other relationships.

"Do you want to go out with the others, or stay here with me?" Molly asked, as she opened the door to the hallway again. She had already resigned herself to not getting any work done that afternoon.

Rosie replied that she wanted to go out, and Molly suggested that she go and help Bea round up the dog and get him ready to leave, too. As Rosie was heading towards the kitchen, she passed Sherlock coming from that direction. He performed a quick deduction of Rosie as she passed by, then ambled over to where Molly was leaning against the living room doorframe.

"I hope you were able to gain John's consent to Rosie staying the night," he said. "Because Bea has taken the presumptive move of setting up her bed."

"On her own?" Molly gaped, picturing their three-year-old running herself over with the roll-out bed.

"William was her co-conspirator," Sherlock replied. "Or possibly her manservant. Either way, it will need to pass a safety inspection later on."

He smiled, slipping his hand lazily around Molly's waist.

"In other news, Teddy has requested to go to the park dressed as a highwayman. Do we have a problem with that?"

Molly gave a sniff of laughter. Teddy had discovered an old riding cape in an outbuilding at the home of Sherlock's parents, which they had gladly let him keep.

"We do not," she smiled back. "As long as he doesn't get too far in character."

"Oh, I don't know," Sherlock replied. "At least it's more up-front than pick-pocketing. Could be an interesting challenge; he and I could see which of us has more success in our techniques."

Molly prodded him in the chest.

"If you both get arrested," she said. "Just remember that I'm only coming for Teddy."

"Hm," Sherlock nodded. "So, I trust the conversation with John went okay?"

She tilted her head to one side with a small shrug of resignation.

"It must feel like being suddenly washed out to sea," she said. "One minute you're paddling in the shallow water, holding hands and just focusing on what's ahead, and then…then your feet just go from under you, and you can't breathe."

"But then the tide ebbs and you get up again," Sherlock murmured.

Molly wound her own arms around Sherlock's waist and drew him slowly around the doorframe and into the living room. Quietly nudging the door almost closed behind them, she arched up on her tiptoes to kiss him, slowly, fondly. It wasn't quite the shoving-up-against-the-door that used to occur between them a few years earlier (although Molly hoped she hadn't seen the last of that), but Sherlock still looked pleased at the surprise of it. When they broke apart, he raised his eyebrow in a question.

"Because I never want to take this for granted," Molly explained. "Never."

Sherlock nodded, thoughtfully.

"All this serves to remind me of the detail that John must have left out," he said, moistening his lips. "That Mary didn't just die accidentally; she took the bullet that was intended for me. John's protecting me. Because if Rosie understood that detail, she would hate me."

It had occurred to Molly, too; if Rosie considered what she knew from a slightly different angle, it could look very different to her – and not just on that score.

"I think he's protecting Mary, too," she said quietly. "If Rosie…if she came to believe that her mum made a choice, well…maybe John's worried Rosie might hate her, too."

"It will come out eventually," Sherlock said. "Nothing stays truly hidden forever. And it's going to have to come from John, or you or me, because Rosie is bright and she's curious, and soon she'll be old enough to go digging on her own – or she might hear it from someone else. We can't allow that to happen."

Molly sought Sherlock's hand with hers. She was reminded of the conversations they had had over the years, usually started by Sherlock, wondering what they would tell William, Teddy and Bea about the past – and how they'd do it. Sherlock's jump from Bart's, his two years in exile? There were ways to tell that story. Sherlock's thrall to addiction, his lapses, his recovery? Molly felt strongly that that one should be told. But what about Charles Magnussen or the truth about Eurus? Those stories were more than a sudden wave, they were potential tsunamis.

But then she hadn't entered into parenthood with Sherlock with her eyes closed.

"We won't," Molly assured him, offering him a hopeful smile. "But maybe we can't just wait around for the next big wave."

Sherlock nodded, his gaze on their joined hands.

"I'll go and see John this evening, once the children are in bed," he said.

"Thank you," Molly whispered, reaching up to kiss him again.

Sherlock glanced behind him as the door began to open, slowly at first, and then more decisively, forcing him to move away from it. A small hand curled around the door, followed by the appearance of a small head.

"What are you doing in here?" Bea asked, again with her trademark suspicion.

"I thought we were going out?" came Will's voice from just behind them.

"They're kissing," Bea reported, matter-of-factly.

An outpouring of exaggerated disgust and gagging noises could be heard from the hallway, which made Molly press her lips together in amusement and Sherlock roll his eyes.

"Actually, I was just about to suggest to Daddy that you could all go for pizza in the café in the park," Molly replied brightly. "That sounds okay, doesn't it?"

Molly heard a small choking noise escape Sherlock, just as the children were erupting into whoops.

"I have to get some work done today, Sherlock," she reasoned, aiming for a tone of justified innocence.

"In that case, Molly, which one of the children are you least attached to?" he queried. "Because clearly I'm going to have to sell one of them to pay for dinner."

Molly grinned up at him.

"Your choice," she replied. "Though best not make it Rosie. She's not strictly ours to sell."

Sherlock gave a brief harrumph but buttoned his jacket and straightened his cuffs in the manner of a man heading into battle. Molly then squeezed past the throng of children and animals (Toby having made a cautious foray into the hallway, too) to reach Rosie, who was busy zipping up her jacket.

"Are you okay now?" Molly asked, quietly.

Rosie nodded, allowing Molly to give her another quick hug.

"Look after them all for me," she told her goddaughter, whose face spread into a smile in response.

William led the charge out of the front door, with Rosie falling into step behind him, followed by Mike leading Bea in a trot, and finally Teddy sweeping out dramatically in his riding cape and homemade mask. When Sherlock reached the door, Molly reached up to pull him in for another kiss.

"Look after her, Sherlock," she told him, placing a hand on his chest.

He regarded her, immediately understood.

"Of course," he replied.

Molly returned to the living room, laptop in hand, just in time to see three curly heads, one blonde one and a pair of very messy pigtails disappear behind a hedge towards the end of the road.

Now, all of a sudden, the house felt far too quiet.