Sadie:

“Everything’s in there.”
Mycroft held the children’s backpack that he’d just been presented at arm’s length, one finger just barely hooked through the top strap. “…What?”
“Everything you’ll need,” Sherlock continued in one fluid, unbroken stream of words as he turned away from his brother and began to leave. “Crayons, coloring book,storybook, crackers if she gets hungry, a handful of legos, her phone, her cup, three bottles of nail varnish, four tubes of lip gloss, her stress ball, she’s already holding her Bucky, two spare dummies–”
“I don’ nee’ those!!!”
Mycroft stared blankly, mouth slightly open, then snapped out of it and started marching after his brother. “…What??”
“–and her sticker book. But don’t let her sweet-talk you into giving her those yet; those are rewards. Oh, and there’s a set of extra pull-ups–”
“SHER’YOCK!”
“…Pull-ups?”
“–just in case. She usually lets you know when she has to go to the toilet–”
The interruption this time came in the form of a low groan.
“–but she doesn’t know you well, so you’ll have to ask and coax her. That’s where the stickers come in.” Sherlock stopped in his tracks once he was out the front door and turned on his heel. He gave Mycroft a broad smile. “I should be back within the hour. Or three.”
Before Mycroft could protest, Sherlock looked around him and stooped to talk to the figure behind him; “And you,” he said, in a much softer voice. “You’ll be a good girl for Mycroft, yes? Of course you will. I promise, we’ll go for ice cream after to make up for it.” Sherlock bent forward and placed a quick kiss on a very hesitant-looking Molly’s forehead. “I’ll be back shortly,” he said again, whirling around to leave.
“…What??!”
“Text me if there’s a need!” he called back over his shoulder and in an instant he was back into the car that had been waiting the entire time, and in the next, was zooming off down the driveway.
Mycroft stood in the door, backpack still dangling in his hand, and gaped at the quickly retreating vehicle.
The purple backpack swung on his finger, and the purple, fuzzy face of the unicorn emblazoned on the front glared at him with what could only be malicious glee.
Mycroft looked down at his side, where his unexpected charge still stood. She too was watching the car as it left, while worrying a lock of hair tightly around her finger. Once it disappeared from their view, Molly looked up at Mycroft with wide, uncertain eyes.
They stared at each other for for a moment, regarding each other, neither one saying or doing anything, until Mycroft decided to break the uneasy silence. “Well…what now?”
Molly stared at him, her hair still twisted around her finger…when her bottom lip started to quiver.
Mycroft could only watch, helplessly, as Molly’s eyes welled up. Next came the sniffles.
“Oh, God.”
~*~*~*~*~*~*~*~*~*~
Things had started off a bit teary, but once Mycroft got Molly inside and showed her the nursery that he kept for John and Sherlock when they were little, tensions eased.
He took her pink cardigan off of her (which was a feat in and off itself, since she was still clutching the odd-looking plush toy that Sherlock had called her ‘Bucky’…an odd choice for a little girl, he thought, with its grumpy expression and half mask and…metal arm?) and hung it on the wall with her backpack. “What would you like to do now, Molly?”
Molly turned and looked him up and down…she still didn’t seem to know what to make of him. All she had heard, he presumed, is what Sherlock or John may have told her…which would explain her nearly bursting into tears at being put into his hands. “Um,” she started, hugging her ‘Bucky’ to her chest. “Um, Sher’yock said, um…tha’d you have craf’s?”
“I have lots of art supplies; Sherlock loves to make things, too. Would you like to see the craft closet?”
Molly’s face finally brightened, and she nodded her head quickly.
“Come along, then.”
*~*~*~*~*~*~*~*~*
“Ohhhhhhh,” Molly cooed, her eyes growing bigger by the second. “You ha’b lots of glitter!”
“Yes, but let’s save that for later, hm?” ‘After I’ve had a chance to glitter-proof the entire house,’ he thought.
“Awww…”
Mycroft thought quickly. “What about the play-dough? Sherlock loves it.”
“Do you ha’b pink?”
“Three different shades. And one has confetti in it.”
Molly gasped; “O’gay!!!!”
~*~*~*~*~*~*~*~
“What’re you mag’ing?”
“An octopus. What about you?”
““Spar’gly y’ibcage.”
“That’s incredibly creative.”
“You ha’b nice han’s.”
“Thank you.”
“C’n I pain’d you nails, My’coff?”
“…”
~*~*~*~*~*~*~*~
“Can I ha’b a s’icker now?!”
“No.”
“Why no’d????!!!”
“Because you didn’t go potty.”
“I don’d ha’b too!!!”
“The wiggling in your seat tells me otherwise.”
~*~*~*~*~*~*~*~
“Molly, dearest, you can have all the stickers you want if you please stop crying?”
“I’d w-was an, an ah-, ah-s-ssid-deeeeeen’!”
“I know, sweetheart, and you’re not in trouble. Look, see? Which stickers do you want in your book?”
“…Th-tha’d, tha’d one, p-p’ease.”
~*~*~*~*~*~*~
“You haven’t eaten since you’ve been here.”
“Bucky wan’s ice c’eam.”
“Sherlock said ice cream later. Neither you or Bucky are getting any now.”
“THA’DS NO’D FAAAAAAIIIIIRRRRRR!’
“Jesus Christ.”
~*~*~*~*~*~*~
“Y-you, you w-won’d tell’im I was ba’?”
“Not if you can use your listening ears and lay down for a rest.”
“Bu’d I’m no’d s’eepy.”
“You’ve been around Sherlock for too long.”
*sniffles*
*sighs* “If I promise to let you make my toes match my fingernails, will you lie down and rest?”
“O’gay!!!”
“Manipulator.”
~*~*~*~*~*~
Molly squealed as she raced down the steps and leapt into a waiting Sherlock’s arms.
Sherlock grunted and hefted her up onto his hip. “You didn’t miss me at all, did you?” he chuckled and kissed her cheek. “Were you a good girl for Mycroft?” he asked, directing the question to her but looking squarely at his brother.
“Y’ah!’ she chirped as Mycroft held his hand up and made an ‘Ehhhhh’ motion.
“Double toppings on your ice cream then,” Sherlock smirked as Molly cheered, and Mycroft rolled his eyes.
“Do you have your backpack? Your Bucky? Your squishy?”
“Yep, yep, yep!”
“Good girl. Tell Mycroft ‘bye-bye’ and thank him for letting you stay with him”
Molly twisted in Sherlock’s arms and gave Mycroft a big grin, and waved her Bucky at him. “Bye-bye, My’coff. I’d was y’ots o’b fun!!!”
Mycroft smiled and waved back at her as Sherlock turned to carry her back to the car. “That varnish is a fetching shade on you, bro.”
“I think Sherlock sounds a bit left out, Molly,” Mycroft called back.
“Ohhhh nooooooo!” Molly clung to Sherlock neck, promising to use all her best colors to ‘make his fingers p’etty too!’ as Sherlock tossed his brother a nasty look over his shoulder and stuck his tongue out.
Mycroft gave him a purple, glittery, one-fingered salute, and smugly stepped back inside his house.