Her name is Gwen, she writes.
Gwen Janine Watson. (Gwen Janine Sherlock Watson, actually - long story. Hope you've forgiven Sherlock and don't mind that she has his name as well as yours.) She's four months old.
I would be glad to introduce her to you - but more glad of a chance to apologize for what I did. For I am deeply sorry. I have regretted my actions so often, and missed you so frequently. So frequently, in fact, that I have composed over four hundred unsent text messages to you since my daughter was born.
You don't owe me anything. But should you ever want to receive a longer apology in person, or to claim all those texts that are rightfully yours, or to meet your namesake - I'll be here. We all will.
She folds the letter around a photo of Gwen and a photo of the whole family, and she sticks it in an envelope.
From below, her daughter cries. Mary gets up from the small desk in her upstairs bedroom, and she walks downstairs.
In the sitting room of 221B, Mycroft Holmes holds Gwen in his lap, bouncing his knees up and down and shushing her gently. It's working; she's quieting, staring at Mycroft with her big blue eyes and forgetting to frown. Mary goes into the kitchen to prepare a bottle.
She passes Sherlock, who is smirking and rosining his bow. "I didn't know you had it in you, Brother," Sherlock says.
Mycroft raises an eyebrow. "I'm seven years your elder, Brother," he says pointedly. "I held you on my lap and shushed you when you were of a similar size."
Sherlock grimaces. "Well, Gwen prefers Paganini to your noises." He begins to play softly.
Mary returns a few minutes later with the bottle to find Gwen watching Sherlock, enraptured. It's a common scene. "I don't know how you can stand to live with him," Mycroft says quietly to her as she takes Gwen from his arms, "but I'm glad you can. He's better, with you and John here."
"Happier?" she suggests.
He raises an eyebrow. "That, too." He sits on the sofa next to her as she gives Gwen her bottle. (She's almost gotten past the disappointment of not being able to successfully breastfeed, but not quite.)
"Here you go, my hungry little beast," Mary says; now that Gwen is here, inquisitive and demanding and occasionally roaring very loudly indeed, they've all agreed she seems more like a little beast than a little dove. ("A nice beast," Sherlock had clarified when John had first applied the nickname. "Oh, like you and John?" Mary had responded with a teasing smile, earning a scowl - but later, she'd heard Sherlock tell Gwen when he thought no-one was listening, "Hush now and drink your milk, so you grow up into a nice strong beast like the rest of us. I've tested it for impurities.")
Mycroft studies her, then adds, "Living here suits you, as well."
She smiles. "Yeah, it really does. Who'd have guessed."
"I'm glad. Though you are missed in your former role. Should you ever feel restless or desire to return to the service, I'm sure we can accommodate you."
"Thank you, Mycroft," she says with a grin. "But so far, living with your brother and John, I've yet to be bored."
"Yes," he says dryly, eyeing Sherlock, "Boredom hardly seems likely to be the biggest risk of living here.
"There's someone from the office who particularly misses you, though," he notes. "She'll be returning to London tomorrow, and I was told to ask if you wanted to get drinks on Saturday."
Mary squeals with delight - but very softly, so as not to disturb their daughter, who is so well-behaved and content at the moment, drinking from her bottle and listening to Sherlock play. When the piece is over, Mary asks, "Sherlock, can I go out for drinks with Anthea Saturday night?" Sherlock frowns but doesn't answer. He sets down the violin and grabs his laptop.
Mycroft raises his eyebrows in amazement. She laughs and says, "Oh, it's not that I need permission. It's just that it will wreck his spreadsheet if I'm not here to put Gwen to bed."
"I'm tracking a number of developmental variables," Sherlock mutters. "Is it too much to ask that we keep the sleeping arrangements to a set cycle so we can reduce confounds?"
"You and John can sleep in John's and my bed that night and keep her in the upstairs crib," she offers, "if that helps." She's pretty sure Sherlock was planning to use his and John's room for an experiment this weekend - babyproofing the flat has meant fewer hazardous substances in the kitchen.
Sherlock frowns, types, and mutters. Mycroft looks like he's just received too much information about how their household functions. She barely resists needling him by explaining in detail when she shares her room with John, or the baby, or both, or neither, and when the sex occurs. But she values Mycroft as a potential babysitter a bit too much for that.
There's the sound of footsteps on the stairs up to the flat, and John walks in.
"How's Harry's new place?" she asks, kissing him hello as he leans down to say hi.
He stoops to give Gwen a quick kiss, too, then says, "Good. Less empty, now that I've helped her move a couple dozen boxes," he adds with a grimace, rotating his shoulder. "It'll be nice to have her nearby." He walks over to Sherlock, still frowning at his computer screen, and kisses the top of his head. Sherlock, absorbed in the spreadsheet, doesn't notice.
"Did you ask Harry about dinner?" Mary asks.
"Yeah, I did - she said she'll be glad to come to dinner next week."
"Excellent," Mary says with a smile.
There's a peaceful lull while John collapses into a doze in his armchair, and Sherlock finishes his spreadsheet adjustments. Mrs. Hudson drops by to fuss over Gwen and bring her a new blanket she's knitted, and Sherlock and Mycroft deduce the origin of the wool and the gauge and imperfections of the knitting needles. After Mrs. Hudson departs, Gwen rediscovers her toes for the dozenth time that day and sucks them happily.
It's almost unbearably domestic until footsteps sound on the stairs again. Lestrade appears in the door.
"A man who's been dead eight years was just murdered," he says, looking at Sherlock. "Will you come?"
Sherlock says, "Of course," then hesitates. He looks at John and Mary, who look at Mycroft. "Go," Mycroft tells them, taking Gwen. "She could use some time with a more wholesome influence."
John snorts, but says, "Thanks," and Mary and Sherlock thank him as well. Sherlock pauses to issue extensive instructions on the care of Gwen - and the keeping of various spreadsheets - until Lestrade says, "Sherlock!"
And they're gone, on the case together.