The first time is Paris. Hot, sultry sunlight clasping skin, moulding its hollows, accentuating its shadows. There is something unholy in the way they both smile at each other.

She is calling herself Calliope, clicking out the 'c', rounding her lips to suckle on the rhythm as 'o' is overwhelmed by the harsher 'p'. The other woman takes her hand, anchoring light fingertips around the column of her wrist, presses a kiss to her knuckles with her dark eyes unblinking, and says 'Call me Irene' in perfect French.

The woman who calls herself Calliope orders them both coffee served in white cups, the crisp edging of lazy waves, clacking on a patterned saucer. Their table is a latticed metal painted parchment, and the sunlight eddies against the table top, and reaches through to dapple in stubby squares in a sentinel line that stretch and elongate around the exposed lines of their legs.

She uses a knife to stab into the Brioche she has ordered, using the primed vicious motion of the first thrust to carry on down and partly separate the pastry into two halves. Later on tonight, her mission will take an unexpected turn, and she will kill a man in much the same fashion; knife in, then dragging down.

The woman, or The Woman as more have come to know her as, takes half of the offered pastry, settling the morsel on her bottom lip before using her pristinely shaded lips to bite down, the white of her teeth seeming for a moment suddenly bizarre and too bright against the ruby of her lips. While Calliope is pushing a knife into a man's heart later on tonight and wiping her stained hands on a ruined charcoal pencil shirt, Irene will be dragging the flat side of a riding crop up a pale naked thigh with a deliberate slowness, that ruby lipstick unspoiled by her exertions.

The two of them talk in French, lightly, flirtatiously, punctuating the conversation with little empty laughs. They lie about their names, of course, and their histories, drawing out pencil-sketched lives that they will crumple up and toss away when the conversation is done.

Calliope talks at length about a brother that doesn't exist: older by three years, living abroad as an investment banker with his fiancée from Australia. Irene taps in with a mention of an Australian sweetheart she once had, sounding fond and reminiscing about personal quirks; she liked Dobermans, the colour orange, plugging in her iPod to the speaker system in her house and listening to indie rock with the sound blaring, dancing with her naked feet tapping out a beat on the kitchen linoleum. Both know the other is lying – Calliope is an only child, and Irene has never had a lover from Australia – , but the dishonesty is heady, tempting, intoxicating under the burnished sun, and for this brief stolen hour, they both act like they can be anyone they want, that they have all the time in the world.

They part slowly, falling out of each other's orbit with something approaching genuine regret. Calliope writes her name in sloping figures, the ink dotting at the tips of the 'l's and making the tail of the 'p' spiky and then a number that is not hers on the back of the café's napkin, sounding out the required 'We should meet up again sometime', and Irene does the same with a number that is equally as invalid. Neither of them will ever call the numbers to validate their inauthenticity, but Irene will think about the afternoon later on, when the sun has sunk down and in the artificial light of indoor electrics she is trailing her fingers over fevered flesh and listening to a woman begging, and she will wonder whether the woman she called Calliope would beg for her mercy, or whether she would be stoic, tight-lipped and glorious, beautiful as she finally unravelled.

For her part, Calliope will keep the card with Irene's number printed on in her jacket inner pocket for several days longer than is professionally necessary. When she shakes off that name and slips into the old familiar identity of Anthea again, she will draw the card out into the day again, glance at it with an unreadable pause, before she throws it away in the bin under her office desk, and carries on typing.

The second time they meet will be after Irene Adler works with the spider called Jim Moriarty, who grows fat and illustrious at the centre of a network unimaginable in scale, and another two months after Anthea has closed the Adler file for good when Mycroft tells her solemnly about Karachi.

This time is not like the first, all teasing and pretence, and they are not unprepared for this trade-off of falsities. Anthea by connection has been briefed on everything the government knows about The Woman and her insalubrious activities, and Irene, as she always is, was very very thorough when it came to researching the Holmes boys and those associated with them, scholarly in her dedication.

It is a meeting of chance, a frivolous flutter of sun amidst an overcast London sky that has Irene taking her coffee under the parasol of an outdoor table instead of inside, Anthea just happening to be striding through Covent garden with a crisp paper bag in hand; within, the Danish is already greasing the paper to an opaque slick: custard for herself, flaked almond for the boss.

She stops dead upon recognising the face sipping on her coffee surrounded by the hustle of shoppers and tourists, and curiosity alone, as well as a latent fondness left over from their last meeting, has her wandering over. She is not overly surprised that Irene Adler is alive and well despite all evidence to the contrary.

Irene, for her part, also quickly puts a name to a face when she sights Anthea looking directly at her. She does not get up, merely replaces her cup into its saucer and gives a wilful smile.

Their conversation, very much like their characters, is bold and to-the-point.

"If it isn't the Iceman's shadow, " Irene purrs as Anthea walks over to her table, hips swaying just enough to be intentionally enticing. She does look sinful, Irene thinks appreciatively, eyeing up and down the tight fit of the blouse, the lines of black trouser leg that only hint at what is being hidden, as she gestures for the other woman to sit on the chair opposite. "My dear, you haven't intruded on a perfectly fine cup of coffee for the mere purpose of dragging me back in irons, have you?"

"Hardly," Anthea responds dryly. "The government has better things to do than to run up old nuisances."

"Nuisance, my dear," Irene makes a disappointed moue, feigning offence, as Anthea pretends to be aloof from the whole thing by ordering a drink from a circling waitress. "And here was me thinking I'd made such an impression."

"You made a lot of paperwork."

Irene waves her hand, dismissing it as a thing of the past, and then smirks, leaning forward and observing the other woman, with her elbow on the table, closed fist propping up her chin. Her hair is twisted up into a French braid, revealing a neckline which is elegant, sleek, touched lightly by the wavering sunshine at the dip of her throat. Anthea thinks on how it would look if she marked it with the signature of her own lips, how debauched that blank pale throat would seem with raw illustrations of purpling red, primal evidence of conquered territory.

"What name are you going by this time?" Irene asks, voice pitched low. It seems a far more intimate question than it actually is, but maybe that is to do with how she words it, husky tones shaping out letters, wetting her lips with an obscene flicker of tongue.

"Enyo," Anthea says, leaning back in her chair and crossing her ankles, cool and frustratingly calm as she takes her drink from the waitress, now returned, setting it down in front of her, but not before taking a sip. She has put her Blackberry away at least, one last tap of the buttons before she slips the device into a pocket, letting it settle against her thigh.

"Ah. Very classical. Goddess of war, yes?" Irene uses her teaspoon to create a liquid swirl in her coffee. "You of course know my name?"

"Of course."

"That is fortunate," Irene smirks. "I'm planning on making you moan it later."

It is true to an extent. Part of this statement is teasing, experimenting with how far she can take this, whether she can unsettle the other woman, but part of it, most of it, is base, selfish and entirely to do with lust. Irene wants to unwind Anthea, part by part, sees it as a challenge, a mark of strength, wants to reveal the hidden places and locked doors of the other woman's body and take her time in breaking in. She wants to mark every raised indent along the landscape of her spine with the burning brand of her lips, see her mouth shape a pained 'o' that is from a pleasure half overwhelming and half unendurable.

Anthea raises a manicured eyebrow – there, a crack, a shatter line across a porcelain mask, and Irene simmers contentedly in her small triumph as she watches, gaze steady like she's glancing along the line of a handgun, taking aim.

"Really? And how are you planning on doing that?" Anthea is giving nothing away, her demeanour a spread of frost after a cold night not yet melting, but that crack is still there, her interest piqued, and Irene thinks about how she wants to feel her curves under her hands and know her by the language of sound and flesh. There is something erotic about sitting across from this woman, who smiles like she's thinking of how to kill her, how her smooth hands have meted out death and brutal violence but are still wrapped daintily around a glass of water, engaged in taking small feminine sips. Irene knows what she likes in a woman. Knows what she wants. And more often than not, she gets it.

"Well," Irene stands, gracefully moving closer to Anthea, who has stood also, pushing her chair back with her face unreadable. The Woman murmurs in her ear, drops her voice; hot air teasing the skin of the other woman's ear. These are her chessboards, her killing floor, her theatre stage, and she knows how to use her body, how to pitch her tone, choose her words, write men and women a fantasy that lasts as long as a fairytale, until the stroke of midnight and then she is gone again. She knows how this game works.

"Firstly, I'd take you back to my hotel room. It's not far from here, just a couple of streets away. I'd watch you as you went up the stairs first, and I'd make sure you knew I was watching. You know of my reputation, you know what I could do to you, how skilfully I could do it, and all of this would be going through your mind as you get into my room, and I lock the door, and you would just stand there as I peel your layers back one by one, take off your jacket, your blouse, your bra…." She breathes slowly, and hears, faintly, ever so faintly, a slight hitch to Anthea's breath. "I'd lay you down on the bed, and run my hands over you, every inch of you, and I'd tell you not to struggle because I've ordered you, and good girls listen to their Mistress if they want a reward. All the things I could do, you can't imagine, and I would do them all; make you teeter on the edge for hours, make you plead and groan and stammer for me to touch you again, and then, maybe if you've been a good girl..."

"I disagree."

Irene flicks her head, interrupted, the reverie lost, pleasingly surprised all the same at the response. This isn't how the game usually goes.

Anthea smirks, and leans in herself, lessening the gap between them, something dark and dangerous in her words, something enticing and forbidden, raw and unrelenting and heady with sex. She is a combatant not without skills of her own, and she plays her own tactics now.

"That won't be what would happens at all," she says in an undertone. "See, I would come back with you to your hotel room, and we'd lock the door, but that's as far as your plans go." Anthea clamps a hand around Irene's wrist, imitating cuffs and her intention is smouldering black in her eyes. "I would hold you down, leaning over you, my body engulfing yours. And I don't need tools or toys or pretty accessories; I'll tie you down with those dainty stockings you're wearing, and just use my hands, my lips… depriving you of your power, your perfect control that you so highly prize, all the pieces of your games stripped down to nothing. I know your reputation, but it would be me marking you, claiming you, and I would make you beg for hours for my mercy, for my pity, before I finally granted it." She pulls back, a wicked smile on her lips. "How does that sound to you, Miss Adler?"

"My," Irene breathes out. This is so much better than she was hoping for. "You do make some promises. Although I do find that sadly it is so often the case that they rarely live up to the excitement they offer."

She straightens her back unconsciously, uses a slim finger to reach up and trail the tip of her fingernail down Anthea's jawline, shaping it with only a gentle pressure exerted, her other hand still trapped in the other woman's manacle hold. "So much talk you see, my dear, and so very very little on the delivery side."

"I can promise you that I very rarely disappoint," Anthea says, and she moves in fully now, crowding space overtly to infiltrate nearly every pocket of air between the two of them.

Irene does not stop smirking. "I'd like to see you demonstrate that."

"I have some personal errands to attend to." Anthea says, almost dismissively, twisting Irene's hand over with her grip so her palm is facing downward, before releasing her, leaving her fleeting legacy in whiter circles of fingerprints which seep away like sand structures in high tide. "But I am free later on tonight. I would hate for you to think I do not keep to my words."

"Well then, my dear," Irene smiles, carnivorous, and her eyes are shamelessly raking over Anthea, thinking on what she might try. What limits she might test, where the skin would look debauched and illustrious raised in a faint welt, whether she could bind those smooth wrists in silk, whether she would unwind that power, gain that permission from her. "I shall await your attentions."

From the handbag hanging irregularly over the intricate back of her chair, she pulls forth a thin card, professionally embossed with the name of a hotel, and at the same time also takes out a pen and scrawls a number across it in a slant of blue ink; the tip of the number '2' illustrated with a curlicue, the edged points of '4' sharp and all straight lines. She finally brings the card to her lips, presses onto it a kiss, all the time her dark eyes never leaving Anthea, before she removes the card, leaving a perfect print of lipstick marking out a challenge in the mould of her lips.

"I look forward to see you." Irene passes the card over. Anthea glances at the information, the name of the hotel, the number, memorising it all in an idle swipe of her gaze, but nonetheless she pockets it to keep as a kind of memento, part of the show they're playing, their piece of theatre, the overture from that matinee played out in the public sphere reserved as a taster for the night-time performance behind closed doors.

"Likewise." Anthea nods, before they stand and part ways, re-joining their own path lines in the world .

They will not come together again until that later hour when Anthea taps thrice on the hotel door with the golden digits of the door number printed just above eye level. She smoothes her demurely chosen lipstick with another rub of her lips together. Her blackberry is locked and on silent in the small clutch she has brought with her.

Irene answers in an ebony lace wrap, stopping at the top of her thighs, the rest of her hinted at through the opaque outlines seen though the lace: the suggestions of lingerie, the wicked surprise of perhaps nothing at all. And Irene purrs that they won't be disturbed, and my, my, she thought Anthea would be here later, doesn't she appear keen, and Anthea smiles without actually smiling, more of that glint in her eyes, and doesn't rise to Irene's power games – noting how the lack of clothing, and displays of flesh is meant to distract her, make her more pliable, more easy to persuade. How quaint.

"Have you been wicked, Miss Adler?" she murmurs, and Irene grins. And it doesn't take longer than a heartbeat before they've both agreed to this, whatever this is, this dangerous meeting, liaisons in the dark, and Anthea steps into the room. Irene locks the door behind her with a sliding click. They will not be disturbed.

"Irene," she will ask the second time this happens, head tilted back to study the ceiling above her. It has helical curls raised in plaster, a dirty white with spiders making families in the cobwebs and bundles of egg sacs in the upper crevice of the room. "What are we doing?"

Irene has propped herself up on her side, the thin sheet only aiding to exhibit the dip of her waist and then the widening of her hips as she leans close to Anthea, using her finger to trace slow sloping patterns across the flat of her navel. There seems no pattern to it, no hint of design, but it is soothing, reassuring, a sense of calm within the entropy she's marking momentarily on skin.

"I don't know." she replies, not looking up from her endeavours, using the tip of her nails to sweep and curl the line she's drawing. "I find that I'm never very good at labelling what is difficult to. Best not to try sometimes."

Anthea nods, and does not ask again. She returns to staring at the ceiling, feeling sticky and sweat-lined and not willing to remove herself from the sheets that cradle cool on her heated skin. Irene goes on drawing her imaginary tattoos, pursing her lips slightly in concentration, humming aimlessly as she does so.

The third time is Catalonia in a yellow painted hotel called La Masieta, with the windows wide open and the sweat on their skin an artwork of lines, the sheets under them a rumpled white as they twist and hiss words in foreign tongues, and all the time seek to get ever closer, conquer a greater battleground than before. The fourth is Helsinki, the fifth Abu Dhabi, where Irene claws her fingers into the base of Anthea's scalp, and pulls on her roots and makes her inhale sharply. The sixth sees Irene call out Anthea's name, feeling centre stage of a spotlight too bright, arching her back and begging for the first time without being asked to, writhing and pleading with her wrists cradled in braces and her legs spread wide open.

The next time it will be Minsk, or Belarus, or Washington, and they owe each other nothing, no allegiances other than the ones they hold for carefully planned moments of release, skin slipping over skin, elbows and knees and rounded edges, each taking control by turns, implicit trust in the conduct of the other. The world falls by the wayside, and they burn, burn, burn and there is always room to blaze brighter than before. And then the near domestic tranquillity afterwards, bandaged in a sensuous haze of endorphins, where Anthea will pad over to the coffee-maker wearing Irene's shirt, the buttons half-done up and in mismatched holes, and Irene will take her half of the complimentary chocolate and eat it slowly and call her 'darling', and they'll both talk about their own lives outside the neutral territory they've made out of broken beds and fractured gasps, their battle wounds displayed without shame in their nudity as they sample the breakfast in bed, talking without ever really saying anything at all.

"Do you know what you're doing?" Mycroft asks her once, the yellowing of the office light not reaching the crevices of the wide room, the curtains closed for a late night, the empty china cups on their desks drained and in need of a refill.

Anthea could deny it, but she won't. She isn't ashamed after all, and there is no point lying even though she wouldn't, not to Mycroft. She respects the man too much for that. She thinks, if he asked her to stop whatever affair she has with the Woman, stared her down and told her this would have to end, she'd probably finish it that day, even though he in turn respects her too much to give her that order.

He is asking from the standpoint of an employer, but his expression is a level different, more that of a friend. Her brother, made out of the covert hours they've not talked of work, when she brings him an unnecessary coffee even when her shift has long since ended, when on the day after a blip in national security that left them out of touch and hectic for hours, he buys her a sleek new blackberry with his own personal number as the only contact preprogramed, not looking at her as he requests that she keep the object on her person at all times. Holmes is not an emotionally vocal man, but she understands him the best she can.

Right now, he is concerned for her safety, not for her reputation, placing the utmost faith in her professionalism without being blind to the possible consequences of her actions. Knowing that she could fall for that woman with the cut-throat smile, and accidently betraying secrets, knowing he would not think any less of her, but all the time, trusting that she won't.

"Yes," she says, and Mycroft does not bring the topic up again.

It's not love, what they have between them. The roots of it aren't in the right place, the climate tundra with not enough water to let it grow into something greater. They work with what they have, each getting out of this something without one or the other fighting for supremacy. They aren't two snarling dogs, who even when the bedroom door is closed and the light dimmed to the lowest setting are trying to tear at the bones of each other's lives, attempting to devour up the portions their teeth can claw at. They don't ask anything that could compromise the other. That is the only unspoken rule of their fragile arrangement. This is closer to being diplomats, business partners, without their transactions being cheap, sordid affairs. They aren't doing it for money, or power, or the upperhand of some universal game. Neither is quite sure why exactly this continues, in Barbados, in Trinidad, in Malmö, on bedspreads and hotel floors and each morning parting again as though the oldest and wisest of friends. They both go different ways, and lie about what route they are taking. Ingrained habits die hard.

This should not work. They should barely fit together. They were not made for a unity with anything. Their smooth edges are all bristles and glass-spun barbs when people get too close, marbled smiles lasting long enough to draw a dagger. They are the contact points of their own personal warfare, the rules of conquest the same on both grounds. Irene tries to tear the world apart a little bit at a time simply because she can, playing her games, her many faceted roles; the Woman, the Seductress, the Lady. She's been written with too many words to her name, too many capital letters, too many adjectives so that now they clash, overlap, tangle up in each other and spread out that way like briar, and Anthea falls in and scratches herself willingly, knowing she can handle it, perhaps kidding herself that someday she might catch a glimpse of the real Irene Adler underneath all her masks. When Irene is with her, when the Woman has slipped a hand around the back of her neck and presses short fleeting imprints of her lips down the her neck to the dip of her collarbone, Anthea feels ungoverned. Like a speeding car, all gleam and growling engine, all motion and basic directions and the unpredictability of stop/start, and she is full from the sensation of the limits of logic. It's based on mutual satisfaction, give and take, offering and supplying, as close to normal as either will probably ever get. They've got something like respect between them, not complete and not perfect, but there is something sprouting in that arid wasteland they call their hearts. They trust each other to an extent, and that's a rare phenomenon in itself.

"Oh darling, we could have been something," Irene ponders once, as Anthea is buttoning up her jacket one handed, the other thumbing the touch-screen to scan a message, flicking through and assimilating the co-ordinates sent through from Mycroft. She will leave her hair down today, she thinks. A precaution.

"Once upon a time," Anthea considers, meeting Irene's gaze. To the right, she can see the window, the clear glazing showing off the Østfold skyline, a vast hungover sky, spiced with the last dots of old stars and the clutching spectre of the moon, now up too late. "Perhaps."

"Don't look so serious, darling," Irene mock-pouts in a childish mimicry. She draws her robe further around her, covering up the smooth lines of her upper thighs, the curve of her stomach. Anthea rakes her eyes over her with a smile as she clips in her earrings. Irene gave them to her . A gift. "I don't feel that I have missed out. We're doing quite fine as we are."

Anthea doesn't reply, using her fingers as a makeshift comb to pull the trestles of her hair down over her shoulders. Covering up the neat circular bruise, a firebrand of mottled purple, just under her ear, making sure it remains hidden from view. It is her trophy, the mark of a victor, her battle bruises from the night before which were shared out in kind; her museum to the now-unimportant past that is fading with the paper-pale moon. Today is shining and new and glowing in cadence and there are promises of more memories in the future to be tattooed on her skin. Beunos Aires, Irene had said, three weeks. Alvear Palace Hotel, room three-twenty. Think you can make it?

Yes, she had murmured, and then had kissed those lips to stop them from talking.

"Women like us are not made for love," she says finally. It is almost as an insolent response, an argument for her case – who is anyone to tell her what is moral, what is civilised, what classes as love and what does not, where the line is drawn in chalk or dug into sand – and Irene makes a hum of agreement in her throat. They've made their own tentative affair right here, in candlelight and moonlight and lamplight, bathed in sweat and shaking, and though Anthea will never write Irene ballads or sonnets, or promise to die for her, she still holds her near as their breathing slows down from an oxytocin high, and together they drift into a numb exhausted sleep.

"How right you are," Irene says, and it's not wistful, but it's a considered statement that is at least thinking of how it could have been different.

She stands up from where she's been lounging on her half of the bed, takes leisurely steps with her naked toes scuffing the carpet, and when she gets to Anthea, she adjusts the lapels of her suit jacket with a careful concern, reaching up, tucking the strands of uncaptured hair Anthea has missed around her ears and pulling it away from her face, affection a soft light in the shine of her dark eyes. "But funny, how close we get, don't you find?"

"Hmm," Anthea replies, and uses the edging of Irene's robe to bring her body closer, lips finding lips, eyes fluttering closed, Irene letting out a contented huff, something like an silky purr made in her throat; Anthea constraining herself to a quick affirmation before departure, her palm sneaking in through the unmanned gaps in the other woman's nightwear to touch a reverent palm over her hips, grounding herself against flesh before as she pulls away.

"Until the next time, darling," Irene's smirk crowds up her vision, and there is only another sharp kiss, a fleeting momentary connection, a tease of teeth against her lower lip, before Anthea is collecting up her satchel and phone, turning away from this bedroom scene, clicking the door shut behind her.

It's not love, she thinks. But strange how far they've got.