It's ten past seven in the morning, but the hairdressers' has been open since six. It's already packed. One chair empties and is filled again within seconds, in accordance with strict appointment times. It is a system that will stand, without exception, until closing time at three this afternoon. The heat, from rinse water, hairdryers and other torturous appliances, from the mass of bodies, is already stifling, and full-bodied with the scent of coffees and mince pies.

And all of this, the opening hours, the rush of business, the seasonal treats, might all be explained by the simple phrase, Christmas Eve.

It's into this seething pit, into this atmosphere inflammable with hairspray ('God forbid,' she thinks, 'somebody tries to light a cigarette') that Molly Hooper edges, hardly able to open the door. It was the only slot she could get, now, before work. She's early. Only by five minutes or so, but she had hoped, at this time of the morning, that might get her out a little quicker. As things stand, she spends the entire five minutes negotiating the smothered coat rack, looking for some small space on which to hang the heavy duty garment bag she carries carefully up from the floor.

Heavy duty not because she has anything to protect, but because the regular ones were made of clear plastic. Because the dress would be just hanging there. Once she gets to work it'll be in her locker, and as she leaves for Baker Street tonight it will be under her coat, but here? To have it on display, and everybody looking at it, waiting to see who claims it, and then looking at her…

And they'd think to themselves, 'Really?'

Molly tells herself not to be ridiculous. Everybody here is thinking of themselves and their own image. They wouldn't look twice at her if she was taking a Valentino evening gown down from those bloody hooks. She won't admit it, not even to herself, but that could be the real reason. That could be closer to the truth. A week and a half of shopping, three returns to the same shop, trying it on, talking herself into it, the distasteful look on the salesgirl's face, saying, "Oh, you're finally taking the plunge, then?" Not to mention four days wages spent on the damned thing. And all of this in order to make herself somehow visible finally. To put on a dress and be transformed into somebody who would no longer blend into the background and… And perhaps to be ignored, even with it still in its protective casing, that could be too much.

She's just found a place to put it when a strong, skinny hand touches her arm. Molly doesn't mean to jump. In a crowd like this silly things like this are to be expected. But she turns to find a smiling face, a little comfort. "Alright, Moll?" A smiling face looking up at her from shoulder level. This is Dallas, named for the soap and not the city and having never so much dreamed of Texas. Dallas is four-foot-eight in height, and about that around the waist, matriarch of a brood whose influence spreads from Aberdeen to Brighton (without going anywhere near Nigeria). In her entire life, she is the only hairdresser Molly has ever trusted to take good care of her.

Dallas points at a line of folded legs and beached-whale bellies, "That sink on the end's free, love. Susan'll get you washed while I finish Mahogany over here." Over her shoulder, Molly sees what must be 'Mahogany', a girl of no more than twenty tanned and painted to that precise shade, playing with her phone in the chair. Dallas, from the roll of her eyes, has no time for her. And it's this little act of casual callousness that puts Molly completely at her ease.

For a while, at least.

You see, she's at the sink, with her eyes shut. Any other day, when the salon is quiet, Dallas washes her hair. Dallas doesn't speak, and Molly is able to drift, and just enjoy the rough way experienced, no-prisoners fingertips rake her scalp and shake her head. There's just something about it which relaxes her. A flashback, maybe, to the ministrations of her bored mother over a lukewarm bath. A job she's done a million times and no longer even questions.

But Susan, a gum-chewing junior brought in for the holidays, Susan knows none of this. She's too gentle, too tentative, for one thing.

It gives Molly too much time to think. Like, if the girl over there playing with her phone gets called 'Mahogany'… Like, if Dallas were to be called away from Molly, and spoke to somebody else… Mousey… But it's ridiculous, of course. Molly doesn't sit and play with her phone and make demands. Molly's never given Dallas any reason to give her any cruel nicknames.

Then again, she's never given anybody any reason to be cruel to her. Hasn't stopped them, though, has it? The worst of it is when the viciousness comes from somebody you'd want to be close to, somebody would like you except they just don't look, and if only you could make them take that close, hard look, if you could register with them, somehow, even for a moment, then maybe something would-

And for another thing, Susan talks. Which would be fine, if she would only talk and prattle on to herself. Molly could ignore that. But Susan, most unforgivable of sins, asks questions, demands reply. Any plans for the holidays? What do you mean you're working tomorrow? And then, finally, more awful than any other insipid little enquiry, "So what is it that you does, then?"

Luckily, Dallas saves her from having to answer that. Mahogany must be finished; she comes over, shoos the confused Susan away from the basin and finishes the rinse herself. Murmuring, under the sound of the shower head and the general babble, "Pay no attention to her, girl." Relief is as warm and clear as the water. Molly raises her hand to ease a drop of it from the corner of her eye. Just shower water, that's all. Just a little drip that bounced and landed there.

Between the basin and the mirror, Dallas says, with a wicked, leering smile and a hand on Molly's shoulder, "Eh, so, tonight's the night, yes?"

Molly blushes, bites down a laugh. "Well," she twitters, as if she's nervous, the way she always does when she's nervous and wishes she wouldn't do it because it makes her sound like a damned schoolgirl and she hates it… "Well, fingers crossed."

Due to Dallas' stature, the chair is low. She shoves Molly into it and holds her down. Over her head, in the mirror, she forces eye-contact, that fiery smile, "You doubting me, Moll?"

Molly grins. She can't help herself. "Of course not."

Dallas flings her hands about, grabbing in between the wild gestures for the hairdryer and the comb and all the bottles and pots Molly never really got the hang of. "Of course not!" she cries. "I'll have you looking like Angelina, girl! Nah, nah! Better than that tacky whore!"

The hairdresser at the next chair stabs a finger at her, "Don't you pretend my Brad's got bad taste!" and the two cackle in perfect chorus until Dallas fires up her roaring hairdryer and sets to work.

Privately she tells Molly, "Your detective fella gonna see what's under his nose tonight. You come and get your money back if he don't."

Molly giggles. Can't remember the last time she really, properly laughed. Long and hard and without reservation, when did she last really laugh? Yes, there's a long day of work to come after this. Death doesn't know it's Christmas. There'll be bodies to open and facts to untangle, blood and gore and the more terrible effect upon those left behind. But if she could just hold on to this, this feeling right now… Oh God, she'd kill to make this impression. She can radiate happiness and confidence now. Even looking in the mirror, she knows she looks better now than she has in days. If he could just look and see her really, properly smiling, rather than just simpering and shy and twittering… If she could just carry something of this feeling through to tonight…

She has a coffee, and a mini-mince pie. In the mirror, she sees the junior emptying box after box of them onto the microwave tray. Even back to front, the words 'low-fat' are unmistakeable. The pies are for all the clients, of course, so it's a totally unfounded fear that makes her hands touch her stomach under the cape, eyes flickering over to the coat-rack, the thick, black garment bag…

"Your figure?!" Dallas cries, as if she'd said something to trigger it. "Your figure, girl?!" So many people are looking by now that Dallas steps back from the chair and grinds her mountainous curves in a shameless circle, to applause and cat-calling. "Problem with all you women," and she points, traces a great circle around the room, accusing every one of them, "y'ain't got a pick of meat on ya!" And now, when the laughter is general and protects them, she turns back, slapping Molly's shoulder. "You'd turn heads in a bin bag, now stop worrying. What are we doing with this mop, then? You just want it straight or-?"

"No," Molly cuts in, far too quickly. "I mean, I don't… I don't really know but… special? If you know what I mean?"

"Say no more."

She doesn't. She closes her mouth and her eyes and says nothing, and lets herself be worked on. Feeling completely safe, feeling cushioned all around with expertise and honesty and close-leaning, matronly 'meat', Molly lets it all take her away. Around and between the noise of machines, she hears the radio, a new DJ coming on for the breakfast show. His first act, in honour of the holiday, is to play I Wish It Could Be Christmas Every Day, and Molly is treated to the incredible sound of twenty-to-thirty women all singing under their breath at once.

Beyond that, the next thing she really hears is the distinctive kissing sound as Dallas sucks her lips in over her teeth, and Molly feels all that warmth and bulk step away from her. Opens her eyes. Then opens them wider, in case she's dreaming. "Not gonna lie to you, girl," Dallas says to her, "But you are some masterpiece, know what I'm saying?"

Molly touches all the height at the front, nervously, delicately, as though it might all fall away to dust at a breath, then turns a little to see the tumbling curls falling down her back. She is, very slightly, open-mouthed. Very slightly unsure. "Oh my God," she murmurs.

Dallas drapes herself over her hunched, tight shoulder, "Worried any?"

Thinking about it, really thinking about it for a moment. Then… "No. Actually, no. And you're sure it'll stay in until tonight?"

Dallas shoves the back of her head, rolling her eyes. All derision, "Stay in until you wash it out, innit?"

It's beautiful. She is beautiful. And if she was shocked to begin with, it's only because it's been a while since Molly Hooper thought of herself as… Well, since she thought of herself. But now she looks at herself in the mirror and she knows, her hair looks great. She has nothing to worry about, nothing to fear. She sits a little straighter.

This could be the answer. After all the pain and the searching, this could be the answer; maybe nobody can see you until you see yourself.

She gets out of her chair, goes with Dallas to the till and pays. A pittance, really, for what she's gotten out of it. There isn't price on the feeling that swells up in her heart and makes her bend to hug the little woman, to wish her Merry Christmas with more feeling and heart than she's felt in a long time, and only wanting to say more. All she can think of, all she can say in her quiet, scared way is, "It's not just my hair, y'know?"

Dallas gives her enough eye contact to say she understands, then bobs her head in the direction of the coatrack. "Nah, s'that dress and all. You showing me or what?"

And where forty minutes ago Molly would have cringed away out of all existence at the mere thought, now she smiles, bright and broad and all over her face. She goes over and, without taking the bag down from its hook, unzips it enough to show. Dallas makes the right sounds, pulls the right face, appreciative and admiring.

Susan from the sink walks by behind them. Though the sight is not meant for her, she still sees it. Says with a cruelty and an unwarranted hate, "Where you going, love, bloody BAFTAs?"

There's a moment, a millisecond, where Molly might wilt.

But a complete stranger, just another woman waiting on the leather couches, reading a magazine, looks up and shouts, "Ignore her! I mean, get a look at her. She thinks Primark is high fashion!" A laugh ripples through the people who can hear it over all the noises. Susan dips her head and skulks off. "Scrooge!" the woman calls after. And then, not thinking of Molly, she just goes back to her magazine.

Molly zips up the bag, says another true and honest thank you to Dallas, and leaves into the snow, covering her head with her scarf. The salon is only five minutes from work, not far enough to warrant a taxi. And anyway, wasn't she told it'll stay in until she washes it out? Just to remember that makes her smile again. The walk is refreshing. It's too early for the night blanket of snow to have been trodden to brown mulch. Everything is crisp and white around her. Clean and pure. How could she fail to be happy? How could she fail to have faith?

A man she doesn't know, walking along with his collar turned up, looks up out of it. Winks and says, "Happy holidays, love."

That hasn't happened to her in a long time.

The night guard, just going off duty as she walks through the hospital doors, says something along the same lines.

She walks through the lab doors and Doctor Crossin keeps his head down, filling out the duty roster from his night's work. "I got through most of them," he starts, "but there's one left. It's alright, he's a straight up-and-down coronary but…" Then he looks up, "I'm sorry, I was expecting Molly Hooper."

"Shut up," she mumbles, and blushes up out of her blouse and to the very roots of her hair. "I'm going for drinks tonight, it was the only appointment I could get at the hairdressers."

"Well, don't get any of the juicy bits near it. No bigger turn-off than lymph in the hair." He's joking, of course. He wishes her Merry Christmas and just leaves, so he must have been joking. He wouldn't have said a thing like that in honesty and seriousness and just left, then.

She tells herself off, for letting everything be so fragile, for taking it all so much to heart. She takes down her lab coat from her locker and hangs up the garment bag in its place. Not afraid of it anymore. In fact, now she wishes she'd just gone for the cheap one. Imagines all the people who pass through, the surgeons and toxicologists and police saying, "Ooh, that's nice" and "Where are you off to, Cinders?" Silly things like that get her happily though her morning's work.

Molly sets up for the autopsy. Gets the straight up-and-down coronary out of his steel pigeonhole and wheels him over to the slab, moves him along. She takes up the first scalpel and makes the standard Y-incision, from each shoulder to the centre of the collarbone, and from the collarbone down the length of the abdomen, allowing her to peel back the skin. But then, as she begins to make notes, she realizes what's next; moving muscle aside, chopping open the sternum. And after that, the chest cavity.

The gaping, bloody, wet, gory, juicy chest cavity.

She shuts off her tape recorder for just a second. Rushes, not to the sink or any of the usual places, but back through to the duty roster and the desk. A hasty minute is spent going through the contents of the drawers until she finds what she's looking for. It's lonely and dried up in a corner, but it'll do the trick. An elastic band.

With the same care she might afford to, say, bomb disposal, Molly gathers the tumbling curls up from her back and twice, loosely, wraps the band around them. Careful to get it into the trough of those waves, so it won't ruin anything.

She's too used to that not to have developed a crippling fear of it; that someday she'll get everything perfect, and then something or someone will come along and ruin everything.

But that won't be today. No, even with the ad-hoc ponytail in, her reflection in the glass of the door still looks great. She touches furtively at the volume again, before she remembers not to get caught preening in mirrors. For once, though, that doesn't shame her. It just makes her smile, as she turns and goes back to the heart attack on the slab. Humming to herself, I Wish It Could Be Christmas Everyday.