It wasn't often that Sherlock Holmes called upon the aid of Molly Hooper when it came to cases. At least when it came to undercover work.

"I don't understand why John can't assist on this one," Molly said, swinging her shoulder bag down onto the empty chair opposite Sherlock. "He and Mary are back from holiday aren't they?"

"Yes, but I need help of the feminine sort."

"And Mary is unwilling?"

He wrinkled his nose, pursing his lips.

"Oh my God, what did you do?" Molly didn't have to be a genius to know that silence from Sherlock on the subject of Mary Watson meant the Consulting Detective was currently in the dog house.

"I may have dyed Sophia's hair a perfectly harmless shade of purple."

"Purple?!" Molly stared, mouth agape.

"The dye was non-toxic, and it washed out immediately!" Sherlock groused, slouching in his chair. "Sophia said she had her parents' permission, how was I to know?!"

"She is only six," Molly said with a laugh. "Of course she'd want purple hair." Molly knew his attachment to his god-daughter was tremendous. He loved the child dearly, and doted on her. He was known to drop whatever he was doing and rush over if Sophia wanted to see her 'Unca Lock'. Still, one could never be sure what would invoke the wrath of a mother, especially when it came to their children.

"Are you forbidden from babysitting?" She asked quietly after a moment.

"No," Sherlock sighed heavily. "But I am on notice. Right now I think it best to give them a wide berth until things settle down. While the dye does wash out of hair, it does not come so easily off of skin." His mouth twitched as he tried to suppress a grin. "John's hands are as purple as that dreadful Telly Monster on Sesame Street."

Molly covered her mouth, barely stifling her laughter.

"All right," she went to the kitchen, putting the kettle on, still laughing. "Enough said, I've got some vacation time owed me, I'll take a few weeks and help you."

"Thank you, Molly."

She turned, hearing her name. Sherlock had taken to thanking her a good deal more lately. In fact he'd been down right lovely. She turned back to the cupboards, taking down mugs and the sugar bowl, missing Sherlock's fond smile as he watched her putter around the kitchen. He liked seeing her in 221b. He asked her around often, more often to help with experiments in the house than to work on cases. They worked well together, and it was the easiest way for him to relax around her. The more often she came, the more comfortable she was, and vice-versa.

It was not a lie when he'd said he was in hot water with John and Mary. But, when he'd explained the case at first to Mary, she had such a knowing look on her face when she suggested he ask Molly for help instead. Mary had a terribly inconvenient way of knowing what was going on in his head. Between them there was suddenly a silent understanding that, while Mary had already forgiven him for dying Sophia's hair purple, she would pretend to be angry with him for a little while more to give him a reason to ask for Molly's assistance.

"So," Molly's voice broke through his thoughts and he looked up to see her holding out a mug of tea for him. "What's the case?"

He took the proffered cup. "It's at a birthing clinic in Peckham. It seems that over a dozen couples who have attended the classes in the past year have later found fraudulent charges on their credit cards."

"Naturally you suspect foul play from the clinic." Molly said as she slipped her shoes off and curled up on the sofa, tucking her legs underneath her.

"Most definitely," Sherlock nodded (having a very difficult time in not being distracted by how well she fit the corner of the sofa). "I need to get in and investigate. Naturally I will need a cover. Enter, you."

"Me?" Molly laughed. "Well, I suppose I could pretend to be pregnant."

"Just so." With that, Sherlock got to his feet, tea set aside. He disappeared down the hall to his room and went rifling through his wardrobe. "Ah! Here," he came back out, holding aloft the article he was searching for. "I've had this for years, never know when there's a need, shall we try it for size?"

Molly stared at the offending garment. "That's a prosthetic belly."

"Yes. You have to look pregnant Molly. I'd suggest going about it the legitimate way but we really haven't that kind of time."

Molly almost hated herself for turning pink. She grabbed the heavy silicon belly from him, hefting it up and buckling it around her waist.

"This is no good," Sherlock muttered, circling her. "Your boobs are too small."

She turned around, glaring at him, mouth open.

"Sorry! Not- no – yours are fine…but not if you're supposed to be pregnant." Now it was Sherlock's turn to be embarrassed, and Molly laughed at his sudden flustered state.

"I do still posses a few tricks up my sleeves, or rather, cups, in this case," she giggled at her joke, and too the blush that further crept down Sherlock's cheeks to his neck. "I'll make sure I look the part. Now, what is the cover? I'm a single mother-"

"No," he interrupted her, this time crossing the room to the mantle to retrieve a box. "I have to be in the building as well, so a married couple having their first child will be more appropriate."

"Whatever you say," she shrugged. If she was nervous, she did not look it, and just for a moment, Sherlock wished for the days when she might have blushed at the thought of them pretending to be married. The fact that his heart was hammering away in his chest at this moment, at the prospect of people believing she was his wife, that she carried his child said more than enough on his feelings for her. He looked at the box in his hands. Well. One couldn't have everything, and if he could not have Molly's love, he would take her friendship, which was so very dear to him.

"Here," he thrust the box at her, head bowed, looking like a sullen eight year old giving a gift to their schoolyard crush. "Rings." At Molly's gasp he looked up, quickly scanning her features. Had he made a bad choice? Indeed not! She was broadly smiling, yet the flash of pain in her eyes did not go unnoticed by Sherlock. Perhaps she was thinking of her own single-hood.

"These are beautiful, Sherlock, truly," she tugged her ring from the box. "Come on, put it on me," she held it out to him.

Taking the ring from her outstretched hand, he lifted her other in his, slipping the cool metal onto her ring finger. It might have been a very nice moment between the two of them. In fact it was a very nice moment. Here they were in his flat, looking deeply into each others eyes, he'd just slipped an (albeit fake) engagement ring onto her finger. They were literally inches from each other. Sherlock could have kissed her. In fact he was thinking of doing just that when suddenly-

"All right, you git, how the hell do I get this stuff off, you've got a bloody lab under your kitchen sink and I'm not leaving until you help me get this off my hands-" John came blundering in, the moment ruined.

John kicked the door shut, then turned to see Sherlock holding Molly's hand, a large diamond ring on her finger, and Molly carrying what could have possibly been twins. "Oh my GOD what have you done?!" John roared.

"It's a fake!"

"It's for a case!"

Sherlock and Molly spoke at once, then glanced nervously at each other, quickly pulling their hands away at the same time.

"Molly and I are infiltrating a birthing clinic in Peckham," Sherlock explained. "We need a valid excuse to get in. Your hands will remain purple for some time, I recommend wearing gloves when you treat your patients, lest they think you've got something."

"And just how long is this supposed to last?!" John cried, frustrated.

"Probably as long as you keep washing with only soap and water." Sherlock looked at his friend's hands. "Try a solution of rubbing alcohol."

Molly rolled her eyes, smiling sympathetically at John. "Non-gel toothpaste and a nail brush," she said. "Should do the trick."

"Thanks Molly," John nodded. He glanced at Sherlock's retreating form down the hallway before stepping closer to her. "You sure you're okay doing this case?"

"Why? Are you offering to step into my place?" she asked, raising an eyebrow. He pursed his lips, frowning at her.

"I've decided you're spending too much time with Sherlock."

"Actually I've been spending a lot more time with your wife," Molly said with a laugh. "Honestly, I'm fine. I'm looking forward to this, rather!" she had the same smile as when she'd told Greg Lestrade that she was over Sherlock. John didn't believe her this time either.

"Go wash your hands, John," Sherlock called from his room. "Molly and I have work to do!"

John made his way to the door, waving at Molly. "Best of luck to you both," he flashed a grin at Molly. "Let me know how it goes, especially Sherlock in the clinic."

"Oh I'll make sure to call you when it's over," Molly laughed. For once, shared medical knowledge between John and Molly made them both laugh, and heartily. Yes, it would be deliciously funny, seeing Sherlock react to a birthing class. It was just too good an opportunity to pass up.

Authors Note: More than a few of you have messaged me to continue this, and I wanted to let you all know that I had already planned on it! I promise there will be more. Generally, if there isn't a 'complete' tab at the top, I plan on writing more, that's my M.O. I'm glad you all are enjoying the ficlet so much, stay tuned for more!