Disclaimer: I do not own the Marvel Cinematic Universe, nor the terrible 'pull out your tooth by tying it to a slamming door' idea.

"Just for the record: I think this is a terrible idea."

"Shh! Don't let him hear you say that! I just got him all pumped up!" Darcy hissed. "Okay, buddy, you ready?" she called.

"Ready!" Sergei called back.

Natasha pushed record on her phone and nodded at Darcy. Darcy grinned.

"Honey, I'm home!" she yelled, and slammed the door.

Sergei was pulled forward by the string tied to his tooth, but the look on his face when he saw that it was finally gone was priceless. "It worked!" he shouted, jumping across the room jubilantly. "Tasha, look! My tooth! My tooth is gone!"

"Never fails," Darcy told him, and he leaped into her arms for a hug.

"Thank you, Darcy!" he said.

Natasha videoed the tooth retrieval, zooming in close so she could capture Sergei's 7 year old fingers trying to undo the knot of dental floss that Darcy had tied.

"I'm gonna go put this under my pillow!" he declared, holding up his prize, the new gap in his teeth displayed proudly. "The Tooth Fairy's gonna have to pony up the big bucks for this one!"

As his sock-covered feet pounded off down the hallway, Natasha stopped the video and was surprised to find that there were tears in her eyes.

"Are you okay?" Darcy asked delicately.

"Yeah, it's just..." Natasha quickly sent the video to Clint. Laura would want to see it. "I wasn't here for the first two teeth. I just feel like I'm missing his life when I'm away."

Darcy made the face that told Natasha she was about to say something uncomfortable. "Well... you are."

Natasha sighed.

"But if you were here all the time like you want to be, then someone else would have to save the world. And... they probably wouldn't be as good at it as you are, so..."

Natasha allowed these words to cheer her a little. "Thanks."

"No problem. You wanna tuck him in, or...?"

"I will." Natasha nodded. "Thank you, Darcy. Sergei's days wouldn't be half as fun if you weren't here to hang out with him."

Natasha had adopted Sergei after Ultron. A lot of kids in Sokovia had lost their parents, and it had been very difficult for her to put him down after carrying him onto the evacuation transport. In fact, he'd clung to her all the way back to New York, unable to sleep unless she was near.

Natasha sometimes worried that having a superhero for a mom wasn't good for him, but he was happy at the Avengers compound, where he had tutors, space to run, and Darcy. She had arrived at the compound with Jane Foster, and often stayed with Sergei when Natasha went on missions. Sergei and Darcy were good friends, and Natasha liked her too, especially when she would stay a little longer after Natasha came home, to watch a movie or have dinner with them.

"Darcy," Sergei called, running back up the hallway from his bedroom. "Are you gonna tell me the Terrifying Tooth Fairy story again?"

"No way," Darcy replied. "Last time you had nightmares and almost woke up and got eaten whole by the Tooth Fairy, and I prefer my friends alive."

"Come onnnn," he wheedled, tugging on her arm.

"Nope." Darcy crossed her arms and turned her head away, overacting as she pretended to secretly peek to see if he was still watching, then turned quickly away again.

Sergei grinned mischievously. "If you don't, I'll tell Tash—"

"Holy wow, that's not going to work," Darcy said, cutting him off with a hand over his mouth.

"Tell Tasha what?" Natasha prompted.

"Not anything," Darcy replied, giving Sergei a 'come on dude I thought we had a deal' look.

"Darcy has a crush on you," Sergei reported from behind Darcy's hand.

"Not cool, bro," Darcy told him. "Tons of bad karma for breaking a pinky swear. Now I have to tell everybody, including Captain America, about the girl you have a crush on."

"Noooo!" Sergei protested.

"Pinky swears are sacred," Darcy informed him, poking him in the ribs where he was most ticklish and making him jump. "Now, go to bed. I hope the Tooth Fairy doesn't gobble you up with all the teeth she's ever taken because of what you just did."

Sergei groaned, but Darcy was having none of it.

"Nope, go." She pointed down the hallway. "I'm sure Tasha will come say goodnight, but now she knows never to entrust you with sensitive information, so at least some good has come of this."

Sergei glared at her, but offered his fist for bumping, and Darcy regarded him with suspicion before allowing a smile to curl her lips. When she bumped his fist with hers, he grinned and trotted obediently back down the hallway to bed.

"Sorry about that," Darcy said as soon as they heard his door close. "Who knew the adopted child of a super spy would be so bad at keeping secrets?"

Natasha smiled at Darcy's blush. "I'm sure he'll get the hang of it eventually," she said.

"Yep, probably," Darcy replied, her eyes anywhere but on Natasha. "I'm gonna... go. Now. Goodnight!"

"Darcy," Natasha called, when Darcy reached the door. "Thank you again, for everything."

"Yeah, no problem."

"Um, hang on. I wanted to..." Natasha shuffled through a pile of papers on the counter, looking for the flyer she had put there. "There's a pretty nice spa in the next town over; I wanted to treat you to a massage or a facial or something as a thank you for hanging out with Sergei whenever he needs someone to keep an eye on him." She found the brochure and stepped over to hand it to Darcy.

"Oh, wow, that's really..." Darcy took it, glancing at the cover before smiling up at Natasha. "You're welcome, and... thank you, I guess."

Darcy reached for the doorknob, but Natasha caught her hand instead. "Darcy," she said. "I like you, too."

Darcy looked a little shocked and a bit disbelieving, like she was the victim of a prank and someone was about to jump out at her and laugh. She cleared her throat. "Like, you like me, like, 'excellent work, colleague, I value your contribution' like me? Or, like, you want to kiss me?"

Natasha smiled and leaned in to answer Darcy's question with her lips.

"Tasha and Darcy, sittin' in a tree, K-I-S-S-I-N-G!"

"Get outta here, you sneaky little voyeur!" Darcy growled, tossing a nearby oven mitt in his direction. He dodged, giggling, and they could hear him running back to his room, and the slam of the door.

"Looks like he'll get top marks in stealth training," Natasha commented.

"Yes, I'm very proud," Darcy muttered, annoyed.

"A good agent reveals only enough information to accomplish his mission," Natasha replied.

"Operation: Get Natasha a Girlfriend seems to have been pretty successful," Darcy said with a smile.

Natasha leaned closer. "He is one of our top agents."

"We'd better get him a bow and send him off to Clint for training; one of these days he'll be a pretty kickass Cupid." Darcy wound her arms around Natasha's neck.

"Mmhm," Natasha agreed, and kissed Darcy again.

Author's Note: You can read my behind the scenes rambling on my blog, iwillwriteyourfic DOT blogspot DOT com SLASH 2016 SLASH 04 SLASH fydl-10-days-of-femslash DOT html