"Mummy seems sad," Emerson tells his father matter-of-factly, in between spoonfuls of the breakfast cereal that Mrs. Hudson had brought upstairs for him (Sherlock hadn't even known that they'd made a dinosaur-themed children's cereal, not to mention with a carnivorous species on the labels, how incredibly inaccurate...).

The detective looks up to cast a glance briefly at the boy. "How did you reach this conclusion?"

Emerson brings another spoonful up to his mouth and chews thoughtfully before finally answering. "She cries during that dancing programme, whenever they eliminate someone. Her hugs last too long. And her eyes look sad," the little boy tells him, certain and sombre and serious even with a box of Ravenous Raptor cereal immediately next to him.

Sherlock frowns at this, and forgets immediately about the sample underneath the lens of the microscope. "Excellent observations, Emerson," he tells his son, although his mind is racing now, reviewing all of his recent data collected on Molly. Was she indeed 'sad'? Had something happened?

And why did he now suddenly seem to feel so strongly about it?

Molly finds it hard to look at couples on the street. Anyone holding hands, pecking another on the cheek, or even those (cringe) openly snogging on the pavement were simply just too much for her to bear. She hadn't always felt this way – in fact, the Molly-Hooper-of-eight-years-past would have felt her heart leap a little bit at the sight of affection, at the sight of love. Something hopefully would coil and uncoil itself in the pit of her stomach, and she would dream (somewhat pathetically) of the day when she would have someone to call her own.

But that day never came, and as the hours and the days and the months of her life pass, she can't help the feeling of disappointment, the stinging bite of emptiness as she continues to be alone.

Part of it, she freely acknowledges, is her own fault. For three years she had carried a torch for a certain detective who could've cared less about her, personally or professionally. She spent those three years ignoring the men who would smile at her in the coffee shops, or who would try to strike up a conversation with her on the train, or who would slip her their business cards under the drinks they would send to her down the bar. Christ, the main reason in her even agreeing to a date with Jim (she refuses to think of him as 'Moriarty') was in the vain hope of getting Sherlock to notice and possibly, just possibly, to make him jealous. Not exactly a fool-proof plan, in the end.

And then Sherlock went and jumped off of the roof of her hospital, and before she knew it, he was back in her flat, and he was shaking, just shaking with adrenaline, barely able to stand let alone sit from the stress and the thrill of it all. She'd gone to fetch him some water, and when she turned around in the kitchen, there he was, his eyes wide and his pupils dilated and before she could make a sound he was kissing her, kissing her like she never, ever thought he would.

Dating after that was, in a word, problematic.

She was too busy at first with her newborn, especially on her own, and after Sherlock came back to the world, it just became too difficult to find someone and to keep them around. She still finds it hard to explain the whole situation to potential suitors ("So this is my son, and this is his father, he comes and goes – please don't be alarmed if he takes any of hairs as a sample for DNA screening"). Most men don't even get close enough for that to even come up.

So now, whenever she spots lovebirds necking at the Tube station, or waiting in a queue at the grocer's, she averts her eyes and wills herself not to think about she feels so totally and completely alone.

Molly comes over to 221B in the (very) late evening hours from St. Bart's to find Emerson asleep on the sofa, Sherlock next to him on the floor. She assumes that the detective is also asleep until she tiptoes closer and notices that his eyes are wide open, focusing intensely on the ceiling above him.

She ignores that for the moment (much like she does with most things he does), and whispers to him: "Help me get him into bed?"

Sherlock redirects his gaze from the ceiling to her in an instant, and the intensity of his stare almost makes her cringe; she swears she can feel his eyes dissecting her, taking stock of her, studying her in ways that she can't even imagine, can't even fathom. And then he blinks, and before she knows it he's on his feet and gently scooping the little boy up into his arms, carrying him up the stairs to the spare room vacated by John after his marriage, Molly following them both close behind.

After nearly four years of watching Sherlock interact with her (their) son, it still makes her heart pang every time she watches Sherlock interact with the boy in a paternal way; it still flummoxes her that a man so utterly incapable of interacting with adults in a respectful and socially appropriate manner can be such a good father, even if he does approach parenting sometimes in his own very peculiar way. She watches from the doorway as he puts the boy to bed, before she advances to place a kiss on the forehead of her sleeping son.

"Goodnight, Emerson," she murmurs, before stepping back and closing the door.

When she makes her way back downstairs, she finds Sherlock standing with his back to her, facing towards the window overlooking Baker Street below.

"Do – do you mind if I sleep on the sofa? I'd like to take him to school tomorrow, and I really don't feel like taking the bus back to my flat." She waits a moment for him to respond, but nothing. She frowns, unsure if he's heard her. "Sherlock?" she tries again, her voice uncertain now.

"Emerson thinks you look sad," he says abruptly, still turned away from her.

This takes her aback – she feels as if all the air in her lungs has been replaced with a vacuum, an absence of oxygen deep in her chest that makes her gasp audibly. "He – he said that?" she manages to whisper, and then she realizes that of course her son would notice, he notices everything, just like his father.

"Yes," Sherlock replies, and now he's turning to face her, his eyes locking with hers. "Why are you sad, Molly?"

Against her will, she feels tears start to pull at the edges of her eyes. "I – I'm not," she tries to tell him, but she knows, she knows he can see right through her.

He steps closer to her, until he's right in front of her, looking down at her with his unreadable gaze. "Why are you sad?" he asks again, softer now.

She squeezes her eyes shut in a vain effort to keep the tears from falling, and wills her heart to stop thumping so furiously in her chest. "I'm just-" she starts, and she can hear her voice breaking, "just a little lonely, that's all."

There's a pause, a very long pause, and Molly doesn't dare to open her eyes, doesn't dare look him in the face because she doesn't think she can take the judgement there, doesn't think she can deal with the pity she might see in his eyes.

And then suddenly she feels his arms come around her, holding her close, and it's the second time in this sitting room that he's surprised her like this (just like that Christmas party, all those years ago). He's pulling her tight against her, his arms firm and his chest warm, and despite herself she finds herself melting into him, pressing her head against his sternum and revelling in the simple comfort that his touch affords her, and she can't even remember the last time she'd been held like this.

"You aren't alone," he murmurs, and his voice rumbles up through his chest, making her shiver from the vibrations. "You have Emerson, and you have me," he tells her, and she can feel the tears start to soak into the fabric of his shirt.

"You won't ever be alone."

Not as light-hearted as the other installments of this little story, but I think that it's an important one. And while I don't think Sherlock would ever be a sentimental type, I think that fatherhood has made him realize that you sometimes do need to show affection, or demonstrate feelings, even though he doesn't always understand that and doesn't do it often.