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Part 1 of The Equation Of Babysitting
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Published:
2025-04-13
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2025-04-16
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The Equation Of Babysitting

Summary:

When John has to attend to a family emergency, he is in desperate need for someone to help babysit his daughter Dahlia. Of course he naturally turns to Sherlock for help, it's unfortunate that the great detective doesn't have much experience with children but it's fortunate that a certain former lord of crime does and just so happens to be visiting him when this crisis happens.

Or, Sherlock and Liam get roped into babysitting for John and Mary and chaos happens.

Notes:

(This is set post New York and they are back in London, and I wrote this as an established relationship fic please be aware there is manga spoilers)

I realise 221B is probably not the best place for a baby to be but William is there so it's okay.

Chapter 1: The Reunion

Notes:

(See the end of the chapter for notes.)

Chapter Text

It was a usual day at 221B Baker Street, and boredom had once again reared its ugly head. Sherlock was sprawled out on the sofa, the newspaper discarded on the floor, his legs draped over the arms. His eyes were closed, but he didn't appear to be sleeping, just deep in thought, or rather, the absence of thought. The silence in the room was deafening, only broken by the occasional sigh from the consulting detective.

“Bored, are we?” came a teasing voice from behind him, breaking the stillness.

Sherlock turned to see Miss. Hudson had come bustling into the room, her apron dusted with flour and a tray of freshly baked scones in her hands. She set it down on the table with a soft thud. 

“Not bored, Miss. Hudson. Just contemplating the sheer lack of stimulating cases,” he replied, his voice smooth yet tinged with a hint of impatience. “You know how I thrive on intrigue.” 

“Right, and I suppose lying there in silence surrounded by crumpled newspaper articles counts as ‘intrigue’?” she chuckled, shaking her head. “You need to get out more, Sherlock. Maybe a nice walk in the park? Or visit that charming friend of yours?”

At the mention of his 'friend', a flicker of something warmer ignited in his chest. “Liam is preoccupied with his- how would you phrase it?- his noble endeavour of educating the young.” A smirk made its way to Sherlock's lips as he rolled his eyes. 

Miss. Hudson leaned against the doorframe, hands on her hips. “You mean he’s hiding out in that large and fancy estate with his brothers? Honestly, Sherlock, you two are like lovesick schoolboys. Can’t you just invite him over?”

“Lovesick schoolboys? Nonsense, Miss. Hudson. We are merely… two men of intellect who appreciate each other’s company.”

“Right. And I’m the Queen of England.” She turned to leave, tossing a glance over her shoulder. “You should write to him. Or I might just do it myself.”

“Please don’t,” he called after her, a laugh escaping him despite himself. 

The door clicked shut, and Sherlock was instantly forced back into his mind of boredom and useless cases. His thoughts ended up drifting towards William. They had spent three tumultuous years together in New York, a time filled with revelations and laughter, but also shadows of their pasts. The weight of their shared history lingered between them, but there was a comfort in knowing they had survived it together. Yet, now with both of them back in London and William under a new guise, their connection felt fragile, like a thread pulled just a little too tight. 

 


 

A few more days passed since then, and a few more cases were turned down for lack of interest. John was beginning to feel the desperate need for inspiration, too, but luckily for the doctor, he had a wife at home and a new addition to the family in the form of a small human. Needless to say, his partner had other things on his mind than sitting with him in 221B, mindlessly filtering through cases.

Sherlock’s thoughts were soon interrupted by a knock on the door, jolting him momentarily out of his boredom-induced coma. He cracked one eye open, listening to the faint murmurs of voices in the hallway. Miss Hudson's soft, feminine tones and a slightly familiar but more formal male voice.

 

He could hear Miss Hudson shuffling through the hallway. “Sherlock, you have a visitor!” she called, a hint of surprise in her tone. “He says you’re expecting him.”

“Expecting him?” Sherlock muttered, running a hand through his dishevelled hair. “I’m not expecting anyone.” 

The door soon creaked open, revealing an all too familiar figure. The person who had been on his mind far too much recently, William James Moriarty, stepped inside his hair now dyed black, a stark contrast to the bright blonde that used to frame his face. He wore a crisp grey waistcoat and an equally dark suit jacket to match this seemingly new and gothic disguise.

“Am I interrupting?” William asked with a playful lilt in his voice.

“Only the mundane. Please, rescue me,” Sherlock said, the flicker of a grin breaking through his otherwise stoic demeanour.

William chuckled, his lips curving into a smile at Sherlock's blunt honesty. The detective's exhaustion was palpable, etched in the heavy lines under his eyes and his slouching shoulders.

He took a few steps forward, crossing the threshold of the familiar Baker Street flat. "Mundane, hm?" he mused, his eyes scanning the cluttered room. "You look like you're on the brink of an intellectual crisis, my dear sleuth."

Sherlock slumped further into his chair, his head lolling back and eyes closing in a gesture of weariness.

"I’m bored," he groaned in response, his voice exasperated. The detective's usual spark of energy and sharp wit seemed dimmed under the weight of his frustration.

"There aren't any good cases. Everything's too obvious, too ordinary. I need something to challenge me."

"I see, so you are mourning the thrill of the chase? No games are afoot, then?" William teased in return.

"Mourning is a bit of an exaggeration; the games have never been less afoot, unfortunately." Sherlock groaned again in response. "You could say I'm missing the excitement. There hasn't been a case worth my time in weeks." He lifted his gaze to William and offered a small smile. "Enough about me, to what do I owe the pleasure of your visit, my dear Liam?"

"I wanted to see you. It’s been too long.” William began, instantly confirming the detective's suspicions that yes. They both still felt the same.

Sherlock was quick to add. “Two months, eight days, and—” 

“Twenty hours,” William finished, his lips twisting into a grin that made Sherlock’s heart race. 

“Good to see that you’ve been counting,” Sherlock concluded.

The exchange of numbers was so precise and was an intimate language only the two of them would understand. It was a dance of precision and memory, a silent testament to the deep bond they had formed over the past few years.

William gave a soft smile as he took a seat on the arm of the chair, his hand instinctively finding its way to Sherlock's messy hair, his fingers gently running through the strands. 

"Precision is everything, isn't it, Sherly?" he whispered, his tone affectionate and familiar.

A small sigh of contentment escaped Sherlock's lips as he leaned into William's touch, his eyes closing once more, this time in pleasure rather than weariness. The physical contact, the warmth of Liam's hand threading through his hair, sent a wave of comfort and familiarity that he had sorely missed. He murmured his agreement, a hint of affection in his voice as well.

"Yes, everything," The detective replied, his hand reaching up to rest on William's, taking hold of it gently.

William let out a small hum in contentment as he felt the detective's hand grasp his own. The familiar feeling of Sherlock's touch sent a soothing warmth through him. He shifted to sit more comfortably, his body now slightly turned towards Sherlock, their proximity closer than before. 

"Boredom never really suits you, does it, Sherly?" The now raven-haired male teased.

Sherlock's eyes opened again, an amused grin finding its way to his lips. He turned his head to look up at William.

"No, it doesn't," he replied dryly. "I wasn't made for sitting around, as you well know."

He let his hand drop from William's, only to reach up and take hold of a loose strand of the dark hair. Sherlock twirled it around his finger, an absent-minded gesture.

"Black, hm?" he commented, his tone casual.

William couldn't help the chuckle that escaped his lips as he saw Sherlock's hand toying with the strand of his hair. "Indeed," he said, a hint of a smirk on his lips. "Quite a change from my usual blonde, wouldn't you say? A new disguise, a new persona… It washes out fairly easily, so if you dislike it, I wouldn’t be completely offended."

Sherlock's lips curled into a half-smile, his eyes still fixated on the strand of dark hair. "It's Different, yes," he mused, his gaze lingering on William's new appearance. "But it suits you,” he admitted, his voice low and sincere. 

The sound of footsteps and the clink of china interrupted their moment as Miss Hudson entered the room, carrying a tray with a tea set.

The two men quickly withdrew their touches, casually maintaining a small distance between them. Sherlock cleared his throat, his expression returning to its usual stoic demeanour.

Miss Hudson set the tea down on the table for them both. "I thought perhaps you both could do with a nice cup of tea while you catch up. Your visit is unexpected, Mr Moriarty, but it's good to see you nonetheless; you look well."

William smiled politely at Miss Hudson, his gaze flickering to Sherlock for a brief moment. The slight distance they had put between them felt like a necessary shield, a way to shield their true relationship from the casual eyes of others.

"Thank you, Miss Hudson," William replied, his voice formal yet friendly. "It's a pleasure to see you as well. I hope I'm not disturbing your day."

"Nonsense! Sherlock tells me you have taken up teaching again?" Miss Hudson inquired, trying to make polite conversation.

He was genuinely surprised that Sherlock had mentioned his new employment, considering he hadn't even mentioned it yet. But he hid this surprise behind a smile. It was only natural for the detective to be keeping tabs on him, he supposed.

"Yes, I've started teaching again," William answered, his tone polite. "At a small private academy, nothing too noteworthy, but it keeps me occupied."

The scent of Earl Grey began to fill the room as the landlady poured out the tea into three cups. 

“Just a quiet life of teaching children about the wonders of mathematics, then?” Sherlock raised an eyebrow and reached out to take one of the cups. "Sounds rather dull."

“Just wait until they discover the mysteries of Pythagoras.” William added, a mischievous twinkle in his eye.“It’s a gateway to far more exciting pursuits.” 

Sherlock's eyes narrowed slightly in mocking disbelief at William’s words about it being exciting. The idea of Pythagoras’ theorems being classified as exciting made him scoff. But he knew William enjoyed it, so even if he spoke badly of the subject, he knew the other wouldn’t take it to heart; if anything, he would come up with a witty remark in response.

"Oh, yes, because the study of triangles is truly a thrilling adventure," Sherlock replied dryly, an edge of sarcasm in his tone.

In this moment, William was very glad that he had taken the time to visit today. He truly had missed the presence of his detective entirely.

"My dear Sherly,” he said, his tone light yet affectionate. "You misunderstand. It's not about the triangles. It's about the patterns and possibilities within those triangles. You should know better than anyone that the real excitement lies beneath the surface."

William took a sip of his tea, his gaze flickering to Sherlock over the rim of the cup. With a look that the detective knew all too well, one that only encouraged him to continue matching him on every level.

“Are you two going to keep flirting? Because if so, I'll just excuse myself." Miss Hudson interjected, her hands on her hips.

“Flirting? I’m merely expressing my admiration for Mathematics.” William replied with mock innocence, but his gaze lingered on Sherlock.

The corners of Sherlock's mouth curled into a subtle smirk at William's comment, his own eyes meeting the other's. And yes, they were most definitely flirting. The banter, the shared looks, the subtle touches, it was all part of this intricate dance between them.

The detective soon offered his input and protested to the comment with a feigned air of innocence. "Merely... intellectual discourse."

Miss Hudson glanced between the two of them and then shook her head in disbelief. "Sure, if that's what you're calling it, I'll leave you both to it then." And with that, she took her cup and headed back downstairs.

William's gaze followed Miss Hudson until she disappeared from the room, the sound of her footsteps fading away. Once he was sure she was out of earshot, he let out a soft chuckle.

"Intellectual discourse, hm?" he repeated, his tone playful. "I suppose that's one way of putting it."

Sherlock set down his teacup, leaning back in his chair. "Of course, it is," he replied, his voice dripping with feigned seriousness. "We're simply discussing mathematics. Perhaps I'm just a fan of triangles."

William's laughter, soft and genuine, filled the air. "Ah, yes, a devout follower of the geometric faith. I can see you now, bowing down to the dedicated theorems and reciting the sacred ratios."

Sherlock chuckled, his smirk turning into a full-blown grin. "Oh, yes, picture me praying at the altar of Pythagoras," he mused, the sarcasm still evident in his voice. "Lighting candles of pi and worshipping the holy right angle."

"And don't forget the weekly pilgrimage to the temple of trigonometry. They have fascinating traditions there. They even offer sacrifices in the form of tangents and secants." William added, clearly enjoying their conversation a little too much now.

Sherlock's head fell back in yet another fit of laughter, which felt very reminiscent of their time in New York together, small moments, intimate moments, inside jokes that only the two of them could keep up with. He was truly unsure as to why the both of them hadn't seen each other over these past two months, perhaps it was that they were both being cautious or giving each other space to navigate their lives now that they were back in London, but being together now made it painfully obvious that they were always destined to return to each other's side, in the most poetic way possible.

"I've missed you," Sherlock whispered. It was alright to express his feelings when it was just the two of them like this.

William's laughter died down, the room falling into a comfortable silence as Sherlock confessed his sentiment. The corners of his lips curled into a tender smile, his heart skipping a beat. He reached across the small distance between them, his hand finding Sherlock's and giving it a gentle squeeze.

"And I, you," William murmured in response, their hands clasping in a silent declaration of their shared intimacy.

The simplicity and comfort of the gesture made something warm unfurl in Sherlock's chest. Being able to hold William's hand again, the feel of his skin against his own, was a reminder of all they had shared. 

Sherlock's gaze remained on their intertwined hands, his thumb gently running across the back of William's knuckles. "You should visit more often," he said after a moment of silence, the words leaving his lips almost as a reflex.

A faint, but knowing, smile tugged at the corners of William's lips. He knew just how much Sherlock meant behind those words, the underlying plea for them to be closer. He squeezed the detective's hand slightly harder, a silent reassurance.

"I should." William agreed. "But you could visit me as well, you know. I'm not that far away, and you're always welcome to come by, especially if your cases are as dull as they have been."

Sherlock relented and gave a small nod. "Fair point," he agreed. "In my defence, I figured that you could use some time to catch up with your brothers. I've been incredibly selfish over the past few years, but our time together is something I will hold dear. I knew it would be odd, stepping away from what we knew in New York to come back here, but if anything, it's made me certain that you are a force I am constantly drawn to, mystery or not."

William listened intently, his heart lifting at Sherlock's words. He found it ironic that the detective thought he was the one being selfish when it had been William who had been stealing him away from everything in New York. He squeezed Sherlock's hand once more, a mixture of relief and affection in his expression.

"If I'm a force that tempts you, then you're a mystery that keeps me intrigued," William replied, a small smile playing on the corner of his lips. "Why don't you show me a few of those very boring cases?"

Sherlock felt light after their confession, and he quickly moved to his feet, gesturing for William to follow him towards a stack of papers on the nearby desk. "I suppose it couldn't hurt to get your opinion on a few things." He spread a few newspapers out over his desk along with some documents.

"This one, for example: a simple case of a missing person. The husband reports his wife missing, claiming she never returned from her morning shopping trip. Of course, the idiot failed to mention that he and the local shop vendor were having a little affair, big surprise, his wife was never missing, she had just left."

He forced a smile and then shuffled through some more pages, flipping through descriptions and notes.

"The next one is a petty theft at a local jewellery store, which turned out to be an internal job done by the poor shopkeeper. And finally, a case of supposed witchcraft, which was just an excuse for a man to skip his business meetings." 

William's gaze scanned the assorted papers and documents. He listened as Sherlock explained each case, and he instantly understood why Sherlock was at his wits' end. They sounded like very simple cases. It’s times like these that the detective probably wished that the Lord of crime was still active just to entertain his brilliant mind with another intriguing mystery, and he would be lying if he said that thought didn’t make him at least a little bit happy.

"Petty thefts, affairs, and witchcraft...?"

"Witchcraft." Sherlock gave a nod.

"Right, yes, those sound riveting." William offered a small sheepish smile.

"Oh, don't they just." The detective rolled his eyes and pulled out a few more newspapers.

The two of them ended up sitting together on the sofa, deep in conversation about some of those said cases. It was hard for them to stop talking once they started, minds equally matched in similar thought processes. Sherlock didn't take any clients for the rest of the day. Instead, he fell into the safe little haven with William and the warmth he felt when they were together.

 


 

The sun was soon beginning to set over Baker Street, and William had felt that he had long since overstayed his welcome. The offer from Miss Hudson to stay for Dinner was much too tempting to turn down, especially since it meant that there was an excuse to stay just a little while longer, but now he knew he should head back before his brothers became too worried.

 

"Well, I've enjoyed my time here today." William lifted himself from his seat and shrugged on his suit jacket.

Sherlock felt a pang of disappointment when he realised William would be leaving. He, too, had enjoyed their time together, but he didn't want it to end just yet. He stood up as well, his eyes following every movement William made.

"You could stay the night." The words left his lips before he even thought about it. "I'm sure your brothers wouldn't mind if you arrived tomorrow morning instead."

The offer caught William by surprise, his eyes widening slightly. He hadn't expected Sherlock to ask him to stay. A part of him wanted to accept, to stay in Baker Street and spend the night with the detective. But his sense of obligation pulled him back.

He shook his head slightly, a small, apologetic smile on his lips. "That's a lovely sentiment, Sherly," he began, his tone gentle. "But sadly, I have a feeling that if I don't return home tonight, I might find Louis breaking down the door to search for me."

"I'm sure I could deal with your brother." Sherlock's voice had a hint of teasing in it, an attempt to keep the light mood going. He stepped closer to William, his eyes meeting the other's for a few moments before he shoved his hands into his pockets, a casual gesture hiding away any feelings of disappointment.

William chuckled, his eyes sparkling with fondness. "I don't doubt it, my dear," he said, his tone affectionate. There was still a sense of yearning in his gaze, a part of him that wanted to stay, but he quelled it with restraint.

He stepped forward, closing the distance between them. He lifted Sherlock's chin slightly "But I think it would be best if I go for now," he whispered.

Sherlock bit back a sigh, his eyes fixed on William's, silently pleading with him to stay just a little while longer. "A few more moments, that's all I'm asking for." He tried to keep his voice steady. "Just a little more of your time, before you go." The thought of a quiet and lonely apartment wasn't very appealing to him after all.

William's resolve crumbled at the sight of Sherlock's pleading eyes. He could feel his desires pulling him closer, the urge to stay and give in to the detective's request.

The hand that had been caressing his chin moved up, gently cupping his cheek. William's thumb ran softly over his skin, his gaze dropping to Sherlock's mouth for a brief moment.

William let out a sigh, his voice barely above a whisper. "You know I cannot deny you anything," he mumbled.

That admission was all it took for Sherlock.

He took a step forward, closing the small distance between them in an instant. One arm snaked around William's waist, pulling him flush against him, while the other hand slid up to cradle the back of his neck. He brought their faces together.

"I know," he murmured against the other's lips, his voice filled with a quiet desire, before finally their lips met.

Suddenly, it was as if the world around them faded away. Time seemed to stop as Sherlock's arm pulled him closer, their bodies pressing together. William's eyes fluttered shut, and he leaned into the kiss, the hand that had been on Sherlock's cheek sliding up to bury itself in the detective's messy hair.

The kiss, which had started soft and tentative, soon grew more intense, their tongues seeking and exploring each other's mouths in a slow, desperate dance.

Unfortunately, their moment didn't last very long when the front door slammed open, and John forced his way into the apartment, clearly out of breath and in a panic. "Sherlock! We-" his words fell short when he realised the position he had caught his partner in.

Sherlock, caught in the heat of the moment, reluctantly broke the kiss, his arm still around William's waist, his eyes flickering to the panting doctor.

He let out a low, frustrated curse under his breath, his expression a mixture of irritation and embarrassment. "John," he began, his voice sharp. "This better be important."

William, who had been equally as reluctant to part from the kiss, was now standing there, his face slightly flushed, his hair a little dishevelled. His eyes darted between Sherlock and John, the heat of the moment quickly cooling off in the face of the doctor's sudden arrival and putting distance between him and the detective. He gave a polite nod of greeting to John, his voice still a little breathless. 

"Doctor Watson," William spoke, trying to maintain a nonchalant tone.

John was still trying to process the sight before him. His eyes flicked between the two men, taking note of the dark-haired strangers' flushed cheeks and dishevelled hair. It was clear that he had interrupted an intimate moment between the two.

"I… I apologise for the intrusion." John said, his voice a mix of embarrassment and curiosity. As he peered through the dimly lit flat towards his partner. "Um- Sherlock, not that I have anything against this, but who is this man?... I thought you were seeing William?"

A quiet look of irritation passed over Sherlock's face. "I am! This blasted idiot still can't even tell the difference between natural and dyed hair," he snapped, his tone curt and sharp. "This,” he gestured towards William. "Is Liam."

Sherlock ran a hand through his hair, trying to fix the messy state it was in thanks to William's fingers being tangled in it just moments before.

John took another look at the black-haired young male, still clearly struggling to make sense of what he was seeing. It was quite the sight before him: Sherlock, the great detective, looking flustered and caught off guard by the interruption. Perhaps it would be best if he kept this story to himself.

"Mr Moriarty?" The doctor questioned, his voice filled with confusion. "I-I am truly very sorry!" He bowed his head quickly. "It's a great disguise!" He tried to sound much more positive and gave him a thumbs-up.

William let out a sheepish laugh at John's bewildered yet enthusiastic response. Despite the awkward situation, he managed to find amusement in the doctor's attempt at kindness.

"Thank you for the compliment, Doctor Watson," he said, a hint of a teasing smile on his lips. "I guess my disguise was more convincing than I intended it to be."

Thanks to John's attempt to lighten the mood, the situation felt slightly less tense. Even Sherlock couldn't help but roll his eyes at the doctor's bewildered thumbs-up.

"Well." Sherlock began, his voice tinged with annoyance. "You barged in here like there was a fire or murder. What was so important that you had to ruin the moment?"

John cleared his throat, his mind still buzzing with a thousand thoughts. But he took a deep breath, remembering his main reason for dashing into Baker Street with such urgency.

"Yes, there was a family emergency, and Mary's aunt has fallen ill. She's in the hospital, and her condition is worsening. You know her parents aren't around anymore, so she holds her remaining family close to her." John lowered his gaze. "Anyway, we need to travel up to York tonight, but we need somebody to watch Dahlia for us. I wouldn't usually ask, especially so last-minute, but as your dear friend and partner, could you please look after her for us?" 

The mention of Mary and her family's situation drew Sherlock's attention, his expression becoming more serious.

At the request to look after Dahlia, the detective took a moment to think. A part of him wanted to protest, to say that he had other plans. Babies weren't exactly his area. He didn't have a lot of experience with them. But the situation seemed much more important than his own desires.

Sherlock let out a soft sigh, resignation evident in his voice. "Fine. I'll look after her. Just... make sure you come back soon, alright? I can't handle a child for an extended period of time."

The relief on John's face was instantly visible. His shoulders slumped, and his tense body relaxed. "Thank you, truly," he said, a sincere tone in his voice. "I'll go and get her. She's with Mary in the cab downstairs." He quickly turned on his heel to head back outside.

When the silence returned, William shifted his gaze to Sherlock, studying his expression carefully. "You don't seem very excited," he commented, his tone neutral.

"Excited is not a word that should be used when referring to babysitting," Sherlock replied, his voice dry. He pushed himself off the wall, a hint of irritation still clinging to him.

He ran a hand through his hair, a habitual action when he was frustrated. "I'm not exactly equipped to handle a child, nor do I have the patience for it."

William stepped forward, closing the distance between them again. He reached up, gently tucking Sherlock's hair behind his ear. "You'll survive," he said, a hint of amusement in his voice. "Trust me, I looked after young children during my time at the orphanage... It's not as hard as it seems, I promise."

"You're making it sound deceptively easy," Sherlock murmured, a touch of grudging admiration in his voice. "But you have experience and an actual fondness for children. I don't possess either of those."

William's hand moved to cup Sherlock's cheek gently. "You underestimate yourself, my dear," he said. "You're intelligent, observant, and despite your claims to the contrary, deeply caring. Those are qualities that can translate well when dealing with children."

"You're biased." Sherlock brushed his hand away and nudged William's shoulder gently. "Stay and help? Send a telegram to your brother's..."

"You want me to be your accomplice in this unexpected babysitting adventure, hm?" William mused, folding his arms across his chest.

"Is that a yes?" Sherlock raised an eyebrow in question. A hint of a smile tugged at the corner of his mouth. "Your presence would make this whole ordeal much more bearable, and besides, you were boasting about how easy it was before."

William feigned a reluctant sigh. "Very well. I suppose I could grace you with my presence for a couple of nights, just to prevent your inevitable demise at the hands of a baby."

A hint of relief washed over Sherlock's face. The idea of having William by his side to help with the task at hand lifted a significant weight off his shoulders.

"Your sacrifice is duly noted." The tiniest hint of a smirk played on his lips. "How very noble of you to save me from the clutches of a wailing infant."

Soon, John returned with his daughter and a bag full of necessities. The tension from the moment before seemed to have melted away.

John gently placed a sleeping Dahlia into Sherlock's arms. "There you go, Uncle Sherlock will take good care of you." He whispered soothingly, pressing a kiss to her forehead before stepping back. "We will be back in two days, everything you need is in the bag just there and again- I can't thank you enough." He looked to his friend with an affectionate smile.

Sherlock held the sleeping child awkwardly, clearly not used to the weight in his arms. He looked down at the girl, his expression a mixture of bewilderment and uncertainty. 

"Yes, yes, I'm sure we will manage," the detective replied, trying to project a sense of assurance he didn't quite feel. He then turned to William, his eyes silently pleading for some kind of guidance.

William could see the uncertainty in Sherlock's eyes. He stepped closer, his hand gently resting on Sherlock's arm. "You're holding her too stiffly," he murmured, his voice soft but reassuring. "Relax a bit, she's a child, not a time bomb."

John let out a laugh after hearing that small jab and he glanced between the both of them, realising that they would be okay as long as they had each other, he was greatful that William was here to help, truly he had been worried that Sherlock would have been out of his depth when he'd asked him to babysit out of the blue like this.

"Well, I'll be off then!” The doctor bid them farewell and hurried back down the staircase to his wife.

With John and Mary gone, Sherlock and William were now left alone in the flat with the sleeping child.

William gently guided Sherlock's arms, showing him how to position the baby better in his arms. His hands were gentle and sure as he adjusted the way the detective held Dahlia. "There, like that," he whispered to ensure he didn't wake her. "You need to support her head a bit more."

Sherlock allowed himself to be guided by William's expertise, carefully readjusting his hold on the baby. "Like this?" he asked softly, his voice hushed as he held the baby a little closer, supporting her head more firmly.

William nodded approvingly, a small smile playing on his lips. "Yes, just like that. See, you're doing just fine," he said, his voice low, a tinge of amusement in his tone. "For someone who claimed to be 'not equipped for this', you're a natural."

A slight flush of embarrassment tinged Sherlock's cheeks at William's words.

"Don't get carried away." He replied dryly, his voice barely more than a whisper. "This is only the first hour. I've yet to face the wailing and nappies." 

William gave a snicker at Sherlock's response, and he feigned a sigh, shaking his head in mock resignation. "Ah, yes, I stand corrected." He reached out to take Dahlia into his own arms and began to rock her gently. "But I'll help you with those too, don't worry."

It was going to be a very interesting 48 hours at 221B Baker Street, and for once, it wouldn’t be because of a mystery or gruesome murder.

Notes:

HELLO! I finally found the motivation the write more. I have ideas that I believe will get me through 3 chapters of this fic, If people enjoy it I'm sure I'll be able to write more, next chapter I plan to write for Louis again because I love writing him. Anyway, I hope you enjoy this I had so much fun writing it and I love these two so much!!
Thank you to my friend @DandelionDreamer for picking out John's daughter's name and listening to me ramble.