A/N: This post was inspired by my request for three-word prompts on Tumblr. savanna-the-redhead suggested "Undercover while babysitting," so this is dedicated to savanna-the-redhead. I had to throw in a reference to the movie Mr. Mom.

Disclaimer: Not mine, it all belongs to the BBC.


Holmes and Watson eyed each other dubiously from their respective chairs.

"Are you sure there is no one else?" Sherlock asked. He tried to keep the desperation out of his voice, he really did, but he suspected a little leaked through.

"I told you," John said, sounding like a 4 on Sherlock's 10-point exasperation scale, "her usual sitter is on her honeymoon, Mrs. Hudson is visiting her sister, and Molly is filling in for an absent coworker. There is no one else." He gave Sherlock a list of important contacts and Rosie's daily routine. "I'll only be a phone call away."

"A phone call and the Irish Sea," Sherlock corrected him.

"I'm sure you'll both be fine," John said fondly. He bent down to kiss his daughter's head. "Be good for Uncle Sherlock, Rosie." He smirked at his former flatmate. "Be good for your goddaughter, Sherlock." John left, laughing to himself.

Twelve-month-old Rosie watched her father leave from her place on John's chair and started to cry. Sherlock immediately got up then picked her up and settled her on his hip, smiling wide. "None of that, Watson," he said cheerfully. "You and I are going to have a marvelous time together. Let's see what Daddy left to eat."

He carried her into the kitchen, which was currently free of experiments and thus spotless. He found containers of store-bought toddler food, none of which looked particularly appetizing to him but he assumed she liked them since she stopped crying when she saw them. When she reached for a container of mashed potatoes and meat loaf chunks, he knew he'd found a winner.

Sherlock had just gotten Rosie settled in her high chair, the food on a baby-size plate in front of her, when his mobile rang. John must have forgotten something, he thought. He pulled it from the pocket of the dressing gown he wore and looked at the display, then grinned at Rosie. "Aunt Molly's calling." He pressed the button. "Hello, Molly."

"Hello, Sherlock," she said happily. "I'm on my way over – I got someone else to cover for Laurel. Can you handle Rosie by yourself for another twenty minutes?"

"You forget who you're talking to, Molly," he said, mock offended.

Molly snickered. "Have you forgotten the Chili Incident?"

Sherlock groaned. "How can I? It has a permanent place in my Mind Palace – the room marked Never Again."

"As it should," she agreed. "I'll be there soon, stay out of trouble. I love you."

"I love you too, Molly." One of these days, I'm going to have to thank Eurus for making me realize how much of an arse I'd been.

He and Molly had been officially dating for two months, ten days, and thirteen hours, not that he was counting. Sherlock pulled a black velvet ring box from his other dressing gown pocket and opened it, showing the ring to Rosie. "See, Rosie? Two carat cushion cut, white gold band, matching wedding ring. If you ask me, anything smaller isn't good enough for your Aunt Molly. Anything larger would be too big for her petite hands. I had the whole proposal planned then she had to work. But now that she's off, perhaps I can make it work after all. You'll be my assistant, Watson?" Rosie beamed at him around a mouthful of mashed potatoes. "I'll take that as a yes."

By the time Molly walked into 221B's sitting room, Sherlock and Rosie were in his chair, watching Sesame Street. She watched them silently for a moment, loving the sight of her boyfriend and their goddaughter having fun together.

"Don't tell your father, Rosie, but that Oscar has the right attitude," Sherlock said, smirking a bit. "Anti-social is the way to go." Rosie babbled happily in his lap.

"Don't listen to him, Rosie," Molly said, smiling fondly as she approached them. "Uncle Sherlock may act like a grouch but he's really a big softie." She leaned down to kiss said softie on the lips then Rosie on the top of her blonde curls.

"How long can you stay?" Sherlock asked softly.

"As long as you need me," Molly replied. "I'm free all weekend."

"Marvelous! I have a new case and I need someone," he smiled down at Rosie, "two someones to go undercover with me."

Molly stared at him. "You want to take Rosie on a case?"

"It's just observation," he said patiently. "I need to see if a man is actually working late when he says he is or if he's cheating on his wife with his secretary, like his wife suspects."

"This doesn't sound very challenging."

"It's a three," he agreed, "but boredom has me revising it to a seven. You and Rosie will be perfectly safe."

"If it's a three-turned-seven, why do you need us?" She gently took Rosie from him and sat in John's chair with the toddler, gently tickling her. Rosie giggled.

"A man with a family is always less conspicuous. Here, you'll need this." He pulled the ring box from his pocket again and handed it to her.

Molly held Rosie with one arm and flipped the ring box open with the thumb of her free hand. Her eyes widened when she saw the rings. "Sherlock…" she whispered. She looked up suddenly. "Please tell me this isn't the ring you offered to Janine."

He groaned quietly. "Will no one ever let me forget that singular instance of bad judgment?" Molly just raised an eyebrow so he went on. "No, Janine kept that ring, though I'm sure she's pawned it by now."

"Dare I ask how much you paid for this?"

He smiled a bit. "The usual three-months' salary. I have plenty of time to get a refund." He got on one knee in front of her, grinning at her wide eyes and slack jaw. "Molly Hooper, will you be my wife for the weekend?"

She gaped at him for several seconds. Sherlock inwardly loved it and couldn't wait for his actual proposal. Finally, she cleared her throat.

"Um, yes, I'll be your wife for the weekend," Molly said, a bit dazed.

Sherlock took the rings from the box and slipped them on her left ring finger. Molly admired how the diamond caught the various lights in the room. Even Rosie was enchanted by the ring.

Sherlock chuckled. "Diamonds are a girl's best friend, even if that girl is a toddler. Now come along, ladies. It's time we were off." He stepped into the hallway and came back with his and Molly's overnight bags. Molly had started keeping a bag at Baker Street for emergencies shortly after the two of them started dating.

Molly eyed the bags as she stood up with Rosie. "You really think it's going to take that long?"

"We'll need to watch the building all night," Sherlock said. "Fortunately, there's a hotel across the street."

He pulled on his Belstaff then took Rosie and put her jacket on her while Molly put on her own jacket. She slung her purse and Rosie's diaper bag over her shoulder then took Rosie while Sherlock grabbed their bags and the three of them went downstairs. Sherlock retrieved Rosie's stroller then hailed a cab.

One uneventful cab ride later, they were checking into the hotel. Molly had to stop herself from writing Hooper instead of Holmes when she signed her name. Thankfully, no one noticed her hesitation.

No one except Sherlock. "You should practice writing 'Molly Holmes' while we're here," he said when they were alone in the elevator, smirking a bit.

Molly rolled her eyes and hitched Rosie up a little higher on her hip. "I doubt I'll have to write my name again before this case is cracked."

When they reached their floor, they walked down the hallway, passing no one, then Sherlock unlocked the door to their room. Molly carried Rosie and the diaper bag in first and looked around. The room was a suite with a large sitting room and kitchen area and a door leading to the bedroom. She opened the door and walked into the room. The duvet on the king size bed was already turned down and a crib was set up a few feet from the bed.

I doubt we'll be getting much sleep, Molly thought. Not with the case at hand and Rosie to watch over.

She left the bedroom to find Sherlock sitting on the couch, his Belstaff hung up and his jacket on the back of one of the dinette chairs, his shirtsleeves rolled up. He was flipping through channels. "Boring." Click. "Dull." Click. "Idiotic." Click. "Didn't we have her arrested last year?" Click.

Molly rolled her eyes and passed Rosie to him. When he was sufficiently distracted by the toddler, she grabbed the remote and sat down next to him. "Shouldn't we be watching for this philandering husband?" She flipped through a few channels until she found Pride & Prejudice.

"I already checked – the building is closed for the day, no lights on at all inside. We'll have to wait until tomorrow."

Molly raised an eyebrow. "I see… Sherlock, shouldn't you have checked the office's hours before we came all the way out here?"

"I did, they must have closed early for some reason." Sherlock grinned down at his goddaughter. "We'll just have to catch him tomorrow, won't we, Rosie?"

Rosie grinned back, babbling. Molly retrieved the toddler's favorite plush rabbit from the diaper bag and gave it to her. She was inordinately proud of herself for only getting distracted by the ring on her finger twice.

Sherlock noticed, of course. "I take it you approve of the ring."

"It's perfect," she said, looking at it again. "It's just what I would have picked. It's too bad it'll have to go back to the store when all this is over."

Unseen by Molly, Sherlock grinned conspiratorially at his goddaughter and would have sworn she grinned back the same way.

They spent the rest of the day entertaining Rosie, snarking at bad telly, and had dinner, all without looking at the ring. At least, Sherlock didn't look at it.

After they put Rosie to bed at John's appointed bedtime for her, they left the door to the bedroom open a crack then went back to the couch. Molly sat down on one end and Sherlock laid down with his head in her lap.

She smiled down at him, amused. "Comfy?" She started playing lightly with his soft curls.

"Mmm, very." He stole the remote then flipped to the 24-hour news channel. "Now I know we had him arrested last year."

Molly chuckled. "Have you ever thought about retirement, Sherlock? About doing something other than chasing down bad guys?"

"Perhaps when there are no truly intelligent criminals left," Sherlock said thoughtfully. "London would then hold no appeal for me. I'd probably buy a small place in Sussex Downs and keep bees." He yawned softly. "I've always loved bees."

"That sounds like a lovely retirement," she said softly. "Everyone could come visit you on the weekends." She started to gently massage his scalp and he moaned appreciatively.

"Not everyone," he murmured, his eyes closed. "Just the important ones." He moved one hand to lightly squeeze her knee.

"And who would that be?" Molly asked fondly. When he didn't respond, she realized he had dozed off. Molly let him lay there like that for half an hour then gently woke him. "Sherlock?"

"Mmm?"

"Time for bed. You don't want to sleep in your designer shirt and trousers, do you?"

He opened his eyes to look up at her, smiling softly. "If it means we could just stay like this, yes."

She smiled back. "I love you, but it's time to get up. We're not sleeping out here."

Sherlock groaned as he got up then lead the way into the bedroom. Rosie was still asleep, one arm wrapped around her rabbit. Molly watched her for a moment, then felt her boyfriend's arms gently wrap around her from behind. She leaned against him, sighing softly.

"Thinking about having one of your own," Sherlock murmured. It wasn't a question.

"Yes, but I don't know if my life will ever be settled enough to have a baby. So many things happen at the last minute, it makes it hard to plan anything." She turned to kiss him softly then left the circle of his arms to get ready for bed.

When they were both in bed, Sherlock pulled her close and softly kissed her forehead. "Goodnight, sweetheart."

Molly blinked at him. He doesn't normally go for terms of endearment. He must be exhausted. "Goodnight, Sherlock."

The next morning, Molly woke to the sound of laughter and giggles coming from the sitting room. She got up and pulled her pink silk dressing gown (a Christmas present from Sherlock) on over her cat pajamas then walked into the sitting room.

Sherlock and Rosie were sitting on the floor in front of the sofa, playing with Rosie's blocks. They both looked up when she came in and greeted her with identical happy smiles.

"Good morning, Molly," Sherlock said.

"Ma-ma-ma-ma," Rosie said.

Sherlock and Molly both turned to stare at her. Rosie's first word had been "dada," and John had never been happier. She also could say "nap" and "bot," but this was new.

Molly blinked back sudden tears as she knelt beside the toddler and pasted on a happy smile. "Not ma-ma, Molly. Can you say 'Molly,' Rosie?"

"Ma-ma," Rosie said. She lifted her arms to Molly.

Molly picked her up, thankful that the child was too young to notice her swallowing hard and blinking rapidly. "C'mon, Rosie, let's get coffee started."

Sherlock stood up. "It's already started," he said softly. "The pot should be full soon. Let me take her, Molly."

"No, it's alright," Molly said softly. She held Rosie to her hip as she carried her to the kitchenette.

Sherlock followed them. When the pot was full, he poured them each a cup then fixed Rosie a bottle.

Molly smiled at him gratefully. "You're so good as a fake father. You'll be an excellent real father someday, Sherlock."

He smiled a bit. "How am I as a fake husband?"

"10 out of 10, would definitely recommend to others as a real husband," she replied, smirking.

Sherlock chuckled then bent to kiss her cheek. "Too bad I'm a one-woman man and thus already spoken for." He carried his coffee to the dinette and sat down then started perusing the room service menu.

Molly blinked in surprise then quickly collected herself and carried Rosie, who was happily sucking on her bottle, and her coffee to the dinette and sat down across from Sherlock. "What looks good?"

After breakfast and morning ablutions were done, Sherlock declared that they should go for a walk around the neighborhood and Molly agreed. He got Rosie ready while Molly put on her most comfortable walking shoes.

When they had navigated their way out of the hotel, Sherlock insisted on being the one to push Rosie's stroller. Molly acquiesced, if only because the sight of Sherlock pushing a stroller warmed her heart.

He really is going to be a good father someday, she thought. Not having the stroller freed her hands so she was frequently gazing at the diamond in the sunlight.

"Only newly-engaged women look at their rings this much, Molly," Sherlock murmured in her ear. "You've been married for two years."

Molly blushed. "Um, right. Well, if anyone asks, I can say I just had it cleaned. Maybe I should push the stroller."

Sherlock obediently stepped aside then pointed out the entrance to a park that was just down the street. Molly took a moment to check on Rosie, who was asleep. Molly chuckled softly.

"Play hard, sleep hard, I guess," she said.

Sherlock nodded. "She gets it from her godfather." He grinned at her as she started pushing the stroller again.

Molly just laughed. "With you, it's more deduce hard, sleep hardly ever."

"Oh, I don't know, I sleep pretty well when you stay the night."

She playfully smacked his chest as her cheeks reddened. "That's true."

They walked into the park and down a paved path that wound around a large lake. Molly relaxed as she took in the calmness of the scene. Halfway around the lake, they sat down at a bench, a little old lady sitting at the other end.

She smiled at them. "Hello. It's nice to see a young family out enjoying this beautiful weather. I don't think I've seen you here before, are you new?"

"We're just visiting," Molly said, smiling. "My husband had a late meeting at one of the businesses here yesterday so we decided to spend the night and see a different part of London." She was amazed at how easily the fib left her mouth.

The old lady looked Sherlock over approvingly as he took a fussing Rosie out of her stroller and gave her a teething biscuit. She grinned at Molly. "If my husband were that good-looking, I wouldn't let him out of the house."

Molly laughed as Sherlock's cheeks turned pink. "I try not to let him out too often."

As the morning turned into afternoon, they stopped for lunch at a café. Molly made sure to sit in the shade so she wouldn't be distracted by the diamond catching the sunlight. They both ordered chicken salad sandwiches and Molly ordered a cup of melon pieces for Rosie to go with her store-bought toddler ravioli. As they ate, Sherlock and Molly talked about Rosie, John, everything except the case.

It's nice to feel so comfortable around Sherlock, Molly thought. When we first met, I could barely get two words out around him. Now look at us, dating. We feel like we've been together forever instead of just two months.

After lunch, they walked back to the hotel. Molly was getting concerned about check out time but Sherlock assured her he had reserved the room for two nights.

"We'll be home before John comes looking for Rosie, don't worry," he said.

Once they were back in their room, Molly decided to check on the building across the street while Sherlock tended to Rosie's dirty diaper. One glance out the window told her something was up. She turned back to Sherlock, her eyebrow raised. "Sherlock?"

"Yes?" he asked, his focus on his goddaughter.

"The building across the street is closed. From the looks of it, it didn't open at all today."

"How strange," Sherlock said as he smiled down at Rosie. Rosie grinned back at him.

"Something tells me you knew it was closed," Molly said. "Yet we're still here instead of back at Baker Street. Mind telling me what's up?"

"Nothing," he said as he made silly faces at Rosie, who started giggling.

"Uh huh." She gently picked Rosie up and set her down on the floor with her blocks, then turned to Sherlock. "What is going on, Sherlock? And don't lie to me."

Sherlock stood up, his face unreadable. "There wasn't a case."

"Then why are we out here?" she asked, utterly confused.

"I'll be needing those rings back." He gently took Molly's hand and slid the rings off her finger. Molly watched it happen but when he didn't let go of her hand, she looked up at him curiously.

"Sherlock?"

"Molly, I bought you out here because I wanted to get away from our everyday lives for a little while without the danger of a case hanging over us. I thought pretending to be on a case would be the best way to do it." He took a deep breath then got down on one knee in front of her.

Molly gasped and Sherlock grinned up at her. "This was all designed so I could propose to you in a way that was wholly original and wholly me."

She laughed weakly. "Well, you've got that right."

He held her left hand in both of his, gazing up at her with all the love she knew was in his heart. "Molly Hooper, will you be my wife, this time forever?"

"Yes!" She dropped to her knees and wrapped her arms around him tightly.

Sherlock held her close for a moment then slipped the engagement ring on her finger, smiling a bit. "I assume this ring will do."

"God, yes…" she murmured, her eyes still on it, then she raised them to his, grinning. "Is it okay if I look at it all the time now?"

"By all means," he said, chuckling. "And I think we'll be able control the chaos enough to plan for a few additions to the family, what about you?"

Molly beamed at him. "I'd love that."