Incessant pounding on his door was what finally roused Sherlock Holmes from his bed.

"Sherlock, get up! The cab is waiting and Molly and I are leaving!" Dragging himself up, Sherlock fumbled for his dressing gown, not bothering to turn on any lights.

The door was yanked open and John, having just raised his free hand to knock again, let it drop to his side.

"Leaving where?" he looked at Matilda in John's arms, then at the bags at his feet. "And why is Matilda not going with you?" John pushed in, setting the overnight bag on the kitchen table, followed by Matilda's pillow and blanket.

"I told you last night when I texted you, Liverpool. Harry's back on the booze again, so we're going there to try and get her into a rehabilitation facility."

"Why can't Mrs. Hudson watch Matilda?" Sherlock asked.

"Because Mrs. Hudson is in Australia, she's been gone for a week…didn't you realize she wasn't here?" John asked incredulously.

"No…my tea kept showing up in the morning."

"Thanks to Molly," John said. "Look, we don't have time argue. Molly and I have to go to Liverpool, find Harry and stage an intervention. Once she's in rehab, we're going to go over her flat, clean it up, and then we'll come home. We shouldn't be gone too long, a week at the most. Here's Gladstone's food by the way." The bulldog had followed his master down the stairs and entered 221b, flopping down in John's old chair with a grunt. "Don't forget to feed Toby," John thrust two year old Matilda into Sherlock's arms, kissed his daughter's cheek and picked up the suitcase on the landing. "Be good Tilly," she waved in response, kissing at her father. Molly was heading down as well.

"Oh good, he's already filled you in, just remember, she's toilet trained during the day, but if she cries at night, get her to the bathroom," she enunciated each word as if his life depended on it, so he nodded, eyebrow raised. "Bed time is by seven-thirty at the very, very latest. No experiments involving acid, fire or dangerous viruses." she said and kissed Matilda goodbye. "Be good for Sherlock, Lovey," she smiled at the consulting detective. "Thank you, by the way, I know it was last minute-" she pressed his cheek as well.

"Uh-"

"Toby should be good for two days before you have to check on him. Ta!" she was already waving, halfway down the stairs, John waiting by the cab.

Sherlock went to the window, setting Matilda on the couch, still confused. Not confused. Annoyed. Why did he agree to this? Obviously not awake when he received the text. What if a case came up while he was watching Matilda? He supposed he could always fashion a harness for her and bring her along. Hm. No. She was at the stage in her life where everything must be touched and or put in her mouth. Speaking of-

"Matilda," he said authoritatively, turning back to the couch. She looked up at him, mouth open, Billy the skull half-way to it. "Put Billy down." She looked at the skull in her hands.

"No!" she said. He frowned.

"Give him to me."

"No! Mine," she insisted and toddled off, Billy the skull in her hands. He pursed his lips, following after her. She wandered around for a while, and Sherlock followed behind her.

"I don't know what you're looking for," Sherlock said to her as she poked into each room. "Your mother brings you here on a weekly basis, nothing is new."

Usually, Matilda was a good baby. Not baby, toddler. She was two, and walking now. Running. Running a lot. Good God, Molly had to chase this little beast everywhere! How was he to get anything done with Matilda constantly running to drop things into the toilet or climb tall things she could easily fall from? He needed to get her playpen upstairs and put her in it, but he didn't want to leave her alone. He settled on bungee cording her to the table for now. Satisfied that she wouldn't move, he hurried out.

He jogged up to 221a, let himself in and looked around, finding her playpen folded up by the couch. He grabbed that, along with her highchair. He looked around the flat once more, searching for anything else he'd need. Toby seemed to be blissfully content in the quiet that permeated the flat, happy for once that there was not a small creature grabbing his tail, ruffling his fur in the wrong direction or trying to make him wear doll clothes. He looked perfectly smug at Sherlock, who only glared at the cat before hurrying back downstairs, kicking the door shut behind him.

He was surprised to see her standing just outside the door of 221b, she saw him and scrunched her face up into a grin, reaching her arms up to him laughing.

"Sherlock!"

Matilda had succeeded in dragging the table halfway across the room, stopped just outside the flat as the table would not fit through the doorway. Sherlock sighed heavily. Well that wasn't going to work. He unhooked the cord, Matilda on his hip he managed to kick the playpen open, setting it in the living room. Placing her inside, he looked around, finding a stuffed dog in her overnight bag as well as a few children's books.

"Here, amuse yourself,"

Matilda, for her part, seemed quite pleased to be in her pen for a time, babbling to herself. Sherlock, relieved that she could not climb out of the pen, or at least showed no interest in doing so, went to go about his morning routine, getting dressed and finishing his tea before sifting through emails, solving a few via text, before turning his attention to his most recent experiment. Sherlock did marvel at his brain sometimes, the ability to work on several different problems while working with his hands was something quite pleasing. It wasn't as interesting as a good serial murder, but then, few things are. He wasn't aware of the time going by until he suddenly was pulled from his thoughts by Matilda crying, and Gladstone hopping down off the chair to go to her side and see what was wrong. Sherlock looked, confused from the child to his watch and then the dog.
"Oh bollocks, you eat on a schedule don't you? How tiresome," he set the blowtorch aside, pulling off his gloves and goggles before crossing the room. "Sorry," he lifted her from the pen and she quieted a moment. "What is it you eat anyway? Your mother said anything," he went to the fridge pulling the door open. They both looked inside.

"Ew," Matilda said.

"Hm." he muttered in agreement. He quirked his brow at the only edible thing in the fridge. Well, it used to be edible. Now it was more of a project: how much mold could grow on a piece of brie before it was consumed. "Takeaway it is," he kicked the door shut and fished through the kitchen drawers for the menus. Setting her on the floor, he sat down across from her. "What do you feel like?" Matilda grabbed a brightly colored one, handing it to him. "Curry it is,"

Sometime later, Matilda having been fed and cleaned up was sitting sleepily on the living room floor, she wore her harness the handle end was clipped to Gladstone's collar so she couldn't go far. She got to her feet suddenly, tugging at her trousers. Gladstone got up with her, following (as he had little choice in the matter) her to the toilet. Sherlock watched, curious. Where was she off to now? He was getting tired of jumping to his feet each time she ran off.

"Oh!" he ran after her just as she was reaching the bathroom. He helped her onto the toilet, suddenly remembering toddlers don't remember to pull their pants down. "Bollocks."

"Bollocks!" She swung her feet, smiling up at him.

"You didn't learn that from me," Sherlock said, removing her from the seat, pulling down her pants and setting her on the seat again.

Six 'o'clock saw them eating left overs from lunch. Sherlock figured out Matilda was quite accustomed to her nightly routine, so after dinner, she climbed off her seat (curry. Everywhere.)

"Someone reeks, and I'm sure it isn't me," Sherlock said to the toddler who was wiping her face (or trying to) with her napkin. He heard a chuckle from the doorway and turned to see Greg Lestrade leaning on the doorframe.

"What are you doing?" he asked, trying not to laugh.

"Molly and John are out of town. I'm…babysitting."

"I can see that," Greg said. "You gonna change her or what?"

"I- yes of course!" he snapped and picked up Matilda, unclipping the harness from her. He looked at the child, frowning. He was aware of the basics, but how exactly did one change a diaper?

"Oh for pete's sake, give her to me," Greg took Matilda from him, "It's almost painful, watching you think," he muttered, finding a diaper in the bag. He laid her down on the carpeted floor in the living room. Sherlock watched over Lestrade's shoulder, quickly cataloging away how to change a diaper. Right. Open old diaper, remove, swipe bottom, fasten new diaper. Easy. Oh yes, and replace trousers. What on earth do babies need trousers for?

Freshly changed, Matilda yawned hugely, blinking.

"Someone is sleepy!" Greg smiled, picking her up, "First you better have a bath though," he handed her back to Sherlock. "That's all you, mate."

"Why are you here?" he asked. "Is there a case?" his voice hopeful.

"Not for you," Lestrade shook his head. Immediately Sherlock's hopeful expression dropped confusion and disappointment swiftly taking over.

"What? Why?"

"Because you've got a kid to watch, and you aren't bringing her to a crime scene!" Greg pointed at Sherlock who huffed in response, rolling his eyes. "I mean it, I'll text you the details, send pictures, but you stay here with her,"

~O~

Train to Liverpool

Molly's head was on John's shoulder when she heard his phone vibrate.

"Sherlock," they both said and he dug his phone out, reading the text.

I hope you appreciate that I cannot take any cases while your spawn is here.

SH

Bloody right you're not taking any cases. And that's no way to talk about your God-daughter.

JW

She smells.

SH

Then bathe her.

JW

Right. How?

SH

Figure it out for yourself.

JW

A few moments later his phone pinged again.

DO NOT LEAVE HER IN THE TUB BY HERSELF, SHERLOCK.

JW

YES I KNOW JOHN.

SH

Sherlock pulled the stopper out of the tub, tossing it over his shoulder.

"You can sit up but apparently you can't sit up in a tub of water," he grumbled, Matilda looked up at him, half naked in the bathroom now. She knew how to pull her clothes off apparently. How the hell was he supposed to wash a toddler then? Mercifully, his phone beeped yet again, this time from Molly.

Just a few inches of water in the tub, Matilda can sit up, just help her keep her balance, don't let soap get in her eyes. Gladstone will probably try and jump in with her. DO NOT LET GLADSTONE JUMP IN WITH HER.

MW

Why?

SH

It turns into a water fight, usually ending when one or the other poops the bath.

MW

Children are vile.

SH

Clean and dry and teeth brushed, he set her in her playpen where her blanket and pillow were. Gladstone looked pitifully at the child, then up at Sherlock, Matilda seemed to have the same idea.

"What?" She stuck her fingers in her mouth, looking at Gladstone, then back at Sherlock. He looked from her to the dog, then nodded. "Oh. Yes. Of course." He picked up the dog, placing him in the playpen as well. "There. Comfy cozy. Now go to sleep." Gladstone wagged his stumpy tail, turned around three times and laid down. He did not put his head down until Matilda had dragged her blanket over, laid her head on his belly, shutting her eyes. Satisfied that the dog and child were comfortable for the night, Sherlock turned aside. "No fighting you two," he said over his shoulder.

He looked at the kitchen, his experiment half-finished, the empty food containers and sink of dishes. He'd clean up tomorrow. Wiping off the tray of the high-chair he threw the rag into the sink and plodded down the hall to bed. Babies were exhausting. He wasn't sure how Molly or John got the energy.

He awoke with a start, Matilda was crying. What was he supposed to do when she cried in the night? Oh! Yes. Toilet. He got up, shuffling out to the living room. Matilda was halfway over the edge of her playpen, crying for the bathroom. She managed to get herself down onto the floor, but the room was dark. She sat there with a whimper,

"Sherlock," she called. Taking pity on her, Sherlock took her hand, leading her down the hall. He sat on the laundry basket, having set her on the toilet (remembering to pull her pants down first).

"I thought you had to go," he said. Matilda beamed at him, swinging her legs as she braced herself.

"No!"

"Matilda. Go to the bathroom."

"No!"

"Go."

"No!" He scowled at her. She imitated his expression before bursting into a fit of giggles.

"If you go to the bathroom, you can play with Billy tomorrow." In a moment he heard liquid hitting the bowl.

The second day proved much the same, Sherlock having a better handle on how to keep Matilda confined, or if not confined (as she was prone to shriek if kept too long in the playpen) then at least restrained. Usually that meant putting her in her harness and clipping her to Gladstone, usually with the former trying to pull the latter. Gladstone didn't move very much except when he needed to be walked, or if Matilda was about to do something inherently dangerous. Lestrade proved true to his word and sent him texts and photographs of the crime scene so that he could still help. Despite not actually getting to go to the crime scene and see things for himself, Sherlock was almost, almost, enjoying this whole babysitting business. Matilda was a fairly good child, she didn't often cry unless she messed in her pants, or if she fell down from trying to climb the bookcase (which John and Molly would never learn of).

~O~

Liverpool – John and Molly's hotel room, two days later

"How are things?" Molly asked Sherlock, phone against her ear. She sat cross-legged on the bed, channel surfing.

"Fine,"

"Fine as in 'we are both surviving' or fine 'I've just fed her, changed her and put her down for a nap'?"

"We've come to a mutual understanding," Sherlock replied.

"Oh dear…"

"She sleeps with Gladstone in the playpen-"

"Sherlock!"

"What? Not good? She likes it. He seems pleased,"

"Her blanket will be filthy!"

"Nonsense,"

"What about when she goes to bed?"

"She sleeps in the playpen." Molly rolled her eyes.

"She's alright though? She's not throwing fits or anything is she? It's our first trip away from her; sometimes it's hard on children."

"She seems fine," Sherlock looked at Matilda; she sat in her usual place on the living room floor, babbling to Billy the skull (having at last learned he does not belong in one's mouth).

"That's good, I was worried for your sake, and I know how you like peace and quiet for your experiments."

"Mm, yes well, I've things to do now, Molly so-"

At mention of her mother's name, Matilda looked up.

"Ma?" her face screwed into an unmistakable expression of one about to burst into tears. She got to her feet, whimpering. Matilda suddenly realized she missed her mother and father dreadfully. "Ma?" she worried her fingers together, her mouth formed in an absolute pout, tears welling in her large eyes.

"Shh," Sherlock said to her, then turned back to the phone. "I have to go,"

"No wait, I have to tell you-"

"Yes, I know, don't let her climb out of the playpen, when she cries bring her to the toilet. I will, goodbye," and he hung up just as Matilda opened her mouth and let out a wail. "Oh…uh…bollocks…" he picked her up, trying to lull her as he saw John do, but nothing seemed to cheer Matilda Watson. Gladstone paced, not quite knowing why she was upset, but that she certainly wasn't happy. It was then that Mycroft showed up.

"Screeching can be heard from the street, brother-mine," Mycroft said, annoyed. "Can't you do something to stop her?"

"I am trying,"

"She needs to be distracted."

"By what?" Sherlock asked crossly.

"Sing her a lullaby," Despite Matilda's crying in his ear, Sherlock turned and stopped.

"Surely you can't be serious." Mycroft shrugged. "What do babies listen to?"

"I don't know…try 'Wheels on the Bus'-"

"No," Sherlock said with such venom that Mycroft raised an eyebrow. Apparently Sherlock had heard quite enough of that song from Mrs. Hudson when she babysat Matilda. "What did you listen to when you were a baby?" Mycroft paused, and then standing straight, put his hand on his heart and sang:

"Rule, Britannia, Britannia rules the waves

Britons never, never, never shall be slaves-

Rule, Britannia, Britannia rules the waves-"

Mycroft's 'lullaby' did nothing to dissuade Matilda's tears, in fact it only made her cry harder.

"My sentiments exactly," Mycroft threw him a withering glare. "Obvious reason aside that you came to mock me, what is it you want?"

"Information," Mycroft removed his other hand from his pocket, holding a flash drive. "Regarding that little escapade in Mongolia,"

"Mm," Sherlock took it with his free hand.

"Don't trouble yourself to make tea, I can't take that infernal racket any longer," Mycroft said and headed for the door. "Best of luck," he paused at the door. "To both of you."

No stuffed animal, blanket, or even promises of sweets would quiet Matilda, and Sherlock was reaching his wits end. What if she never stopped? Good grief. Then John and Molly might not trust him with her anymore.

Not that he wanted to keep the child.

It was simply that she didn't talk back when he explained his theories to her. Yes. That was it.

"Oh!" Sherlock was struck with a sudden thought. He opened his laptop, tapping out a quick text to John while he logged onto Skype. In a few moments the screen blinked on, and John and Molly were sitting together in the frame. Matilda looked confused, rubbing her teary eyes with her fists.
"Hello sweetheart," Molly smiled.

"Hey baby girl," Matilda squealed long and shrill, clapping her hands. She stood up on Sherlock's lap, puckering her mouth she kissed the computer screen, much to John and Molly's amusement. "Thank you baby-girl," John laughed.

"Lip marks on my screen," Sherlock muttered. He handed Matilda the skull and she sat down, proceeding to tell them in toddler-speak of the events that day.

"Sherlock why's she got her harness on?" John asked, frowning at the screen.

"What? No reason."

Sherlock humored parents and child for a good hour and thirty minutes, letting Molly fill him in on what was going on in Liverpool (he could have guessed from John's haggard appearance that it was difficult this time, getting Harry into rehab). Finally, Matilda's head was starting to nod; she rested her head against the table, arms under her cheek. Molly understood this time was what Sherlock had been waiting for, so she and John whispered goodbye and thanked Sherlock again before logging off. Silently, he shut the laptop, carefully lifting Matilda against his chest. Instantly, she curled against him and he stiffened a moment. He'd held her before of course, often, in fact. But rarely did she ever fall asleep in his arms, rarer still did she cuddle him as she would her father, rightly so, after all, Sherlock was not the parenting type. Nonetheless his heart softened as the littlest Watson curled against him, head on his shoulder. Setting Billy on the desk, he crossed the room, seating himself on the couch, carefully stretching out.

~O~

As the week wore on, Sherlock came to realize that Matilda seemed to believe she was capable of everything Sherlock was. She wished to be a part of everything he was doing, whether drinking tea, or watching the effects of snake venom on a duck (children liked fluffy animals right?). She was less pleased about that, and turned away, squirming out of his arms. She liked most to watch what he was doing at the kitchen table, or sit on his lap while he went over case files. If he was doing the latter, she sat on his lap, talking to Billy while he did research and emailed or texted Lestrade solutions. If it was the former, she was strapped into her highchair and he let her hold beakers while he measured and recorded data. She liked best when something went wrong. Sherlock reacted in a most amusing way, sometimes messes happened, clouds of funny smelling smoke, or bubbly liquids spilled and foamed at the table. (Sherlock had draped her in a smock and goggles, her high-chair pushed away to a safe distance, just in case). At one point something did go terribly wrong and he snatched her up, high-chair and all and fled out to the hallway, Gladstone underfoot. He left her briefly to open a window in 221b and then returned to the hallway.

"Don't tell your mother," he said, coughing a little from the choking fumes.

"Okay."

He took her and Gladstone for a walk, (each on their respective leashes) grumbling about the tedium of it, until Matilda found a bumblebee and tugged him by the hand, wanting to follow it. Carefully, Sherlock cupped his hand over the insect, letting Matilda study it.

"Did you know that the blood as in other arthropods, is carried in an open circulatory system?" he asked and Matilda commented on how pretty the bee was. "The body organs, dorsal aorta, muscles, etcetera are surrounded in a reservoir of blood, and pulsing contractions of the dorsal aorta create a weak circulatory force," most of the words were lost on the toddler, but by the time they reached Baker street again, 221b sufficiently aired out, she'd learned to say "dorsal aorta" with only a little trouble.

John and Molly returned to Baker Street the next day.

"Dare we see if they've destroyed the place?" He asked. Upstairs they could hear Sherlock talking, Matilda's babbling and the house smelled of rotten eggs.

"Too much sulfur in that one-" they opened the door to 221b to see Sherlock in his dressing gown, Matilda sat on his shoulders, holding onto his hair, watching over his head as he pointed at different beakers. "Smell this one-" he held it up to her nose and she leaned over.

"Ew!"

"Say 'disgusting'-"

"'Scusting," she wrinkled her nose.

"Dis-gust-ing."

"Dis-gust-ing!" Sherlock smirked.

"Yes it is, what you are smelling is sulfur, and once mixed with water it turns into sulfuric acid which is-"

"Sherlock!" John and Molly both gasped.

"Not to be played with," he finished, looking at them innocently. "What did you think I was going to say?" he set the test tubes down. "I knew you were there, you stink of public transport and cleaning fluid." Matilda saw her mother and let go of Sherlock's hair, reaching. Carefully he lifted her from his shoulders, passing her to Molly.

"Hello darling," she kissed her forehead and Matilda returned the kisses,

"Dorsal aorta!"

"What?" Sherlock was fighting back a tiny smile.

"Bees. She was…curious about bees…" he muttered.

"She wasn't too much trouble was she?" John asked, having received a hug and kiss from Matilda.

"No more than usual." Gladstone, seeing his master was back, galumphed off the chair, wagging his tail before heading over to wait by the door.

"I'm sorry we were so long," Molly said. "You must have had to turn down so many cases,"

"A few," he replied. "I solved most of them from here, even with Lestrade's incompetency with a camera phone; I managed to piece together the evidence."

"Well, I'm sure you'd like your peace and quiet now," Molly said. "We'll take her upstairs so you can get on with your experiment."

"Yes," Sherlock said quickly, and gathered up her bags. John, meanwhile, had been looking at the flat. Matilda had been a very busy little girl while they were gone. Several drawings decorated the wall by the window, the largest being two stick figures (one with a long blue scarf), some very odd looking bumblebees and an indistinguishable circle-head…thing. "She was trying to draw Billy," Sherlock said. John was quiet for a moment, he looked from the consulting detective to Matilda and then Molly.

"You know…" he said slowly. "You and Matilda can finish your experiment…Molly and I have to run out to the shops for dinner and food for the cat…" Sherlock did his best to put on a mask of indifference. He shrugged.

"If it's easier," he replied nonchalantly. "I usually just harness her to Gladstone and let her wander.

"Mmhm," John said with a knowing grin. Molly set Matilda down.

"We'll be right back, we'll bring you a treat," she promised her. Thumping across the floor, Matilda scurried to Sherlock who picked her up, swinging her up onto his shoulders again.

"Get some milk while you're out," he called.

"Anything else?" Molly asked as John rolled his eyes.

"Tin of beans if you think of it," he was already setting goggles on his head. "Goggles," he held up a pair to Matilda who slid them over her head.

"Goggles,"

"Holding tight?"

"Yes!"

"Then pay attention," he said and launched into his explanation of sulfur. Molly and John smiled, pleased.

"Don't blow the place up, yeah?" John called as they headed down the stairs. "Or gas the place out?"

"Did that!" Matilda called after them.

"Shh!" Sherlock hissed. "No, no we didn't. Of course, we practice all measures of safety, honestly John, we are not babies!" and he slammed the door after them.

"Yeah!" Matilda yelled.

"Are you paying attention?" they heard Sherlock through the door.

"Yes,"

"Good, smell this?"

"Dis-gust-ing!" Sherlock laughed, and it rumbled in his chest.

"Do you remember the lullaby Mycroft taught you?"

"Yes!"

"Who's Mycroft?" they heard him ask.

"Dumb!" Sherlock laughed harder. Carefully, they peeked in the door. Matilda was on his shoulders still, holding onto his hair and both of them, (one enunciating less than the other since she didn't know most of the words) with matched gusto sang:

"Rule, Britannia, Britannia rules the waves

Britons never, never, never shall be slaves-

Rule, Britannia, Britannia rules the waves

Britons never, never, never shall be slaves!"