The next fortnight passes swiftly, and for the first time since we left London, Oxana seems calm and focused. She's naturally secretive, an archetypal lone wolf, and planning an assassination with me is not easy for her. It isn't easy for me, either; murder is murder after all, even if the intended victim is a horrible person like the Pakhan. But we've both kept going. Oxana has begun to share her thoughts with me, and I've managed to ignore what she dismissively refers to as my "civilian guilt," and concentrate on practicalities and logistics. I've always been good at that.

I'm touched by how hard she's trying to make our collaboration work, and more than that, to make our relationship work. She has no instinct directing her here. She knows how to excite, manipulate and hurt me, but despite the fact that we've lived in each other's pockets for the best part of a month, she still finds my feelings impossible to read. I catch her sometimes, gazing at me with her sea-gray eyes, trying to access my emotions. I find this so heart-rending. I can't imagine how lonely it must be to have your nose forever pressed against the glass separating you from other people. To be eternally out in the cold, trying to look in.

The Pakhan's regular ports of call are Zoya's apartment, a clinic in Nevsky Prospekt where Zoya goes for Botox shots and he for rejuvenation injections, and the Elizarova bathhouse in Proletarskaya. Meetings with the Kupchino Bratva brigadiers are either conducted at an Ossetian restaurant named Zarina, where a private room is reserved for the Pakhan and his guests, or at the bathhouse. Occasionally Dzabrati also entertains at home, with Rushana acting as hostess to gang members and their families. At intervals he visits his cardiologist at a private clinic in the city center. He has a heart condition, believed to be atrial fibrillation, for which he takes Digoxin tablets.

I'll make her feel my love, even if it kills me.

Asmat Dzabrati, the Pakhan, is sixty-nine years old. He lives in an apartment in a massive, gray seventeen-story building on Malaya Balkanskaya Ulitsa, near Kupchino Metro station. He owns several apartments there, which are occupied by, among others, his four bodyguards, his ex-wife Yelena, and his sister Rushana and her husband. He also leases a small apartment behind the Fruzensky department store, a short drive away, where he keeps his "sugar baby," a twenty-four-year-old Ukrainian woman named Zoya whom he met through an introduction agency. His family and Yelena disapprove of this relationship, and refuse to acknowledge Zoya, so she never visits the Malaya Balkanskaya building.

So Oxana goes alone, which is how she prefers it. On a couple of occasions she's disappeared for over twenty-four hours at a stretch, returning cold, hungry and dog-tired. At these times I know better than to even try to talk to her. Instead I run her a bath, bring her cheese and cucumber sandwiches and cups of tea, and put her to bed.

All the intelligence we acquire goes into a file, which we scour continuously for recurring patterns. So far we've found none. For all his old-school leadership style, the Pakhan is wary as a fox, and according to Oxana well versed in counter-surveillance. Arrangements and appointments are invariably made at the last minute, decoy cars are used, and his drivers always vary the routes that he travels. As far as we can discover he never uses public transport.

This information has been provided by Dasha, and has been confirmed by surveillance operations mounted by Oxana. I've been involved in some of these, but always at a distance. Mostly I remain by myself in the apartment on Stachek Prospekt, collating and processing information. I'd like to be out there with Oxana, but she's afraid I would get lost or attract attention in some way. She's probably right. I have a terrible sense of direction, and when I was sent on a course with A4, MI5's watcher department, I struggled embarrassingly, and could never get the communications protocol right.

We're looking for cracks in this facade. Vulnerabilities that we can exploit. I've decided to think of the operation as an intellectual exercise, rather as I used to view my activities at MI5. When I found myself in pursuit of Oxana I lost this sense of distance and became over-involved. With this project I'm determined to re-find my objectivity.

"Why don't you have a bath?" I ask Oxana. "I'll run one. We can get in together."

"Not until we've figured it out."

"Has Dasha told you exactly why she wants the Pakhan eliminated?" I ask Oxana.

"Not until I've figured this out."

"Whatever."

We're in our bedroom, sitting in dusty velveteen armchairs, working through murder scenarios. Oxana's reaction to problem-solving seems to be to suspend all activity relating to hygiene, and she's looking particularly grungy this morning. Her hair is standing out from her head in a crown of greasy spikes, her jeans are in shreds, and the grimy pink sweater from the Prekrasnaya Nevesta warehouse, which she has stolen from me and worn every day for a week, is giving off a deathly smell.

"She doesn't need to."

"She wants to run the bratva?"

"Will it be a problem that she's a woman?"

"She sees that he's weakening. Getting older, losing his grip. So she has to make her move, because if she doesn't, one of the others will. It's just how it works."

"It shouldn't be, but it will be. Women are very poorly represented in the field of Russian organized crime. Dasha told me the statistics and they're horrifying."

"And then what happens?"

"As soon as the Pakhan is dead, Dasha calls a meeting of the other brigadiers and announces that she's in charge. No one will say out loud that she was responsible for killing him, but everyone will know it, and they'll also know that if they give her any shit they'll be taken out too."

"So we're --"

"Yes, pupsik, we're doing a good thing here."

I'm not convinced. But here we are. As Oxana says, if we don't take Dzabrati out, someone else will. So we might as well accept the contract, get our papers and money, and disappear. I'm concerned that if we stay here too long, word of us will somehow get back to the Twelve.

"We could, but it would be difficult. These big Soviet apartment blocks with the narrow corridors were designed for easy surveillance of everyone coming and going. There are two elevators serving the building, both very slow, and there's always one boyevik at the street entrance and another on the ninth floor, where the Pakhan and his people live. Also, Dzabrati is never alone in his apartment. There's always a bodyguard. Add in family members, kids… It's not impossible, nothing's impossible, but there have got to be easier options."

"Possible. He's driven there two or three times a week, usually in the late evening. A bodyguard takes him up to Zoya's apartment, waits outside while he does whatever he does to her, and then walks him back to the car."

"Let's review our options," I suggest. "Are we sure we can't get into his building?"

"OK. Zoya's place."

"That's so disgusting. He's what? Forty-five years older than her?"

"Poverty's disgusting, Eve. Believe me, I've been there. As well as the flat she probably gets a generous allowance, like thousands of dollars a month, and instead of working as a cleaner or a cam-girl in some shithole in Ukraine, she gets to spend her day getting beauty treatments and buying nice clothes."

"But is that how you think of yourself? As bisexual?"

"Still gross."

"I don't think of myself as anything, but technically, I guess, yeah."

"Says the born-again bisexual."

"So you don't want to have sex with a man again? Ever?"

"Is that what I am?"

"Fuck you, Oxana. Seriously, fuck you."

"I doubt he's up to anything too heavy. He's got that heart thing, and if she's smart she'll be able to control him. I knew this girl at university who had a rich sugar daddy. He gave her everything: money, clothes, holidays… And he never even touched her. She just had to do herself with sex toys while he watched, and that was it. Like she said, she'd have been doing that stuff anyway."

"So what are you saying? That you still want to have sex with guys?"

"Yeah. Except that she has to be available to creepy old rabbit-face whenever he feels like sex. And I truly hate to think what kind of sex he likes."

She shrugs. "There are worse sensations."

"Isn't it? We've both had sex with men, after all."

"I don't want to have sex with anyone except you."

"Well, whoopee for Russia's incorruptible justice system. Are you going to get in touch with her?"

"Interesting."

She flicks a glance at me. "Because it's so much more fun bullying you, obviously. You know I asked Dasha to ask around about Lara?"

I fall for it, of course, as she knows I will. "Why can you never, ever, ever say anything nice?"

I don't answer. The only news I want to hear about Lara is that she's dead.

"I did, anyway. And apparently she's been released from Butyrka for lack of evidence. Her case isn't going to court anymore."

"No. Why would I do that?"

"You're always going on about her."

"Only to make you jealous, dumbass. Lara was good at sex, but she was quite stupid. I remember when we were in Venice, having dinner at our hotel, and I ordered us the lobster risotto, which was like the specialità della casa, and the sommelier asked us what wine we'd like and Lara said she wanted Baileys Irish Cream. I mean I'm sorry, but that's just disgusting. We were kissing later on and I could taste it on her tongue."

"Thanks for that little detail. I've been trying not to think of you and her in Venice."

"It is right. And I'm definitely not eating pineapple pizza."

"How do you get into the building?"

She shrugs. "It happened. And I have to admit that I do like pineapple on pizza."

"You didn't 'get' me into bed."

"I jumped. I wasn't pushed."

"Oh, you think not?"

"Oh boo, you prude. How I ever got you into bed I don't know."

"I'm not sure I'd want to try it, even in Paris."

"I've found out that there's a single man living on the second floor who teaches at one of the universities and is regularly visited by one of his female students. I know both their names, and I could pretend to be a friend of hers with an urgent message for him. That would get me inside. Then I could immobilize him, and take things from there. Not ideal, but possible."

"I'll take you to Hank's, in Paris. It's super-delicious."

"We'll see about that. But back to Zoya's place. Getting inside the apartment when the Pakhan's there would be hard; the door's reinforced and there's a high-definition security camera. There's no way he'd let Zoya buzz a stranger in. Much easier to shoot Dzabrati and the bodyguard inside the building but outside the apartment, in one of the public areas. Ideally when they're leaving, and walking from the apartment to the elevator."

"Is that right?"

"That really is disgusting."

"The restaurant?"

"Exactly. We've got to find a solution that doesn't involve killing the bodyguards or any of the other soldiers. Dasha will never be able to keep the gang's trust and loyalty if they know she's been responsible for the death of their colleagues. Basically, we've got to get the Pakhan alone, and eliminate him without anyone seeing."

"Witnesses would definitely be bad news."

"There must be a way."

"Again, possible. I could walk in, shoot the Pakhan in the face, do a couple of the bodyguards before they can react, and fuck off fast. But big, popular restaurants like Zarina are bad news. They're crowded, they're well lit and there's CCTV. It would be messy, and there would be a lot of witnesses."

"He's alone in the banya, we know that. And defenseless."

"And how do you suggest that I, or we, get into the bathhouse? On the days he goes it's men only."

Oxana frowns. "I spent hours in there on one of the women's days. I know the layout of the entire place. I checked out cupboards, ceiling cavities, ventilation ducts, everything like that, and there's literally nowhere to hide. The place is well over a hundred years old, built in Tsarist times, with mosaics and classical statues. And there are customers everywhere."

"Well, women on the day I was there. But yeah."

"Naked guys with towels around their waists."

"So no guns."

"It's next to impossible to conceal a gun in a bathhouse."

"Why?"

"Oxana, please, just tell me."

"OK. You go in through the street entrance, pay your money at the ticket desk, and go into a big changing room with lockers, where you leave your clothes and collect your towel. Then you go through to the steam rooms. These have fireboxes in them, like giant ovens with hot rocks inside, and wooden benches round the walls where you sit. There's a bucket, which you fill from a tap and pour into the firebox through a hole. This produces the steam which raises the heat."

"Like a sauna?"

"Same. Except everything's bigger. And it's more sociable than a European sauna, where everyone just sits in silence. Then there's a kind of cooling-off room with steel pillars and marble slabs where you can get a massage, and people smack each other with birch twigs, which is supposed to be good for the circulation." Oxana folds her arms. "Eve, you know all this, I've described it to you before."

"Tell me the routine again."

"Hot or cold?"

"A slice of Napoleon cake."

"I'm listening."

"Bear with me, OK? I've got an idea."

"OK, two."

"What did you have?"

"No. But since we're never going to get in there on a men's day, I don't see the point."

"Just one slice?"

"OK, there's also a room with a small plunge pool."

"I know you have. Tell me again. I'm just trying to figure something out."

"There's a tea room with a samovar. You can get cakes and blinis and stuff."

"So you wouldn't mind necessarily going back there? And taking me?"

"What else does the place offer?"

"But?"

She turns round. "It could work. If Dasha can get us everything we need, it could definitely work."

"Cold. You go there from the steam room."

"Pretty good."

"How big is it?"

"Good quality?"

"What do you think?"

So I tell her. Afterward she sits there for a minute, unmoving. Then she walks slowly but agitatedly to the window, making fluttering gestures with her fingers.

"It's just for one person. About a meter and a half deep."

"But it would take both of us. You'd have to be part of it. So…"

"Are you ready to do it? Killing's a one-way door. There's no going back."

"So?"

"I'm ready."

"Oxana?"

"Fine. Run that bath."

She stares at me for a heartbeat, and nods. "OK."

With the plan finalized, and the arrangements made, Oxana and I suddenly have time on our hands. We go for long walks together, especially in Kupchino, the outlying district from which Dasha's gang gets its name. It's a tough place, a wilderness of deteriorating concrete housing blocks intersected by motorway viaducts and frozen canals. Cut off from the city by an industrial sprawl to the north, the windy streets resemble an abandoned moon colony, but with little sign of a police presence or CCTV cameras we feel safe here. This is Dasha's fiefdom, and when the monolithic gray outlines of the housing blocks soften in the rose-pink twilight at the end of the day, it's almost beautiful.

"Yes?"

"Try not to be such a bitch. We could be a good team."

Much of our walking is done in silence. Sometimes we don't speak for an hour, just march side by side beneath cold skies criss-crossed with power and tram cables. We are learning each other. Sometimes I look at her and she's there with me, fully present; sometimes she's blank-eyed, in a dimension all her own. She's trying hard to be considerate, even though it doesn't come at all naturally to her. So she'll suddenly stop beside me on the pavement and gently wipe the snow from my face with her gloved hand, or ask me odd, sweet questions like whether I'm happy, or want a cup of tea. Seeing the determined, slightly perplexed look in her eyes at these moments I want to hug her, but I know that this would infringe her rules about attracting attention in public. So I tell her, truthfully, that I'm happy. I don't think about the killing that lies ahead. I think about now, and the two of us, and the tiny, elusive glimmer of her kindness.

We leave the apartment at midday for Kupchino station, and take the Metro two stops northwards to Moskovskaya. Our vehicle is waiting for us outside Alfa Bank, as agreed. It's a Gazelle ambulance, about ten years old, with the interior fixtures stripped out but with emergency lights and siren still in place. According to Dasha, "ambulance-taxis" like this one are regularly hired by wealthy business types who want to beat St. Petersburg's traffic jams and get to meetings on time. With their sirens blaring and their lights blazing, they can thread their way through the worst gridlocks.

It's Monday, nine days later, and Dasha has just learned that the Pakhan has ordered his driver to take him from the apartment on Malaya Balkanskaya directly to the Elizarova banya. This works well for Oxana and me. We have everything we need in place, and it's already snowing heavily this afternoon, which will compromise the effectiveness of the CCTV cameras in the streets surrounding the bathhouse.

Pulling on latex gloves we take the keys from the top of the rear wheel, where the owner has left them, and open up the Gazelle. After checking the equipment, we change into official blue ambulance-crew uniforms, and pull on our wigs and cotton caps. Oxana's wig is a garish henna-red, mine peroxide blond. Oxana drives. We've left ourselves plenty of time, so she takes the slow lane on the eastbound motorway, impassively negotiating the busy traffic. She radiates calm, her eyes betraying nothing except anticipation. As for me, I'm all over the place. One moment I'm intensely focused, with my surroundings vibrant and pin-sharp. The next everything is flat and two-dimensional, and I'm so distanced from events it's as if my life is being lived by someone else.

To my horror I get a low-battery warning on the phone. Three percent charge remaining. Fuck. I tell Oxana, my heart sinking. She doesn't waste time getting angry with me for forgetting to recharge it, but just nods, all focus. The seconds and minutes crawl past, agonizingly slowly. Two percent battery charge left. The Pakhan will not visit the plunge pool, where the camera is hidden, until he has been through all the steam rooms. I touch the app icon, and a grainy image of the pool fills the phone screen. There's someone in the pool, a big guy, wallowing like a whale, and definitely not the Pakhan. He hauls himself out and vanishes. His place is taken by two older men who descend the ladder one by one, briefly immerse themselves, and leave.

We're in position by quarter to two. Oxana parks in the narrow street that runs alongside the Elizarova banya, thirty meters from the entrance, and we put our feet up on the dashboard and wait for the Pakhan's arrival. My heart is slamming in my chest, and I feel weightless and nauseated. He arrives just two minutes before two o'clock, climbing from a black Mercedes SUV, and I switch on my phone to access the app controlling the microcamera that we planted in the bathhouse three days ago. The motion-activated camera is the size of my thumbnail, and it's held in place by a blob of chewing gum the size of a cherry stone.

There's now one percent of the battery charge remaining, and the pool's empty. Another few minutes and the phone's going to die. I feel sick with dread. Fear of letting Oxana down has eclipsed all thought of our real purpose here. We stare at the tiny screen. Oxana's breathing is steady. Her wig, which smells of ancient sweat, tickles my cheek. A figure enters the microcamera's field at the same moment that the screen goes black.

I take a firm grip on the defibrillator unit. It's the monophasic type, at least twenty years old, and heavy. Oxana pushes open the side door of the Gazelle, we hit the pavement running, and seconds later burst through the entrance of the banya. There are two male reception staff sitting at a desk behind a low pile of folded towels. Seeing us they half-rise, and Oxana yells at them to stay where they are. They look uncertain, but our uniforms represent officialdom, and they obey.

"Go," says Oxana, grabbing the first-aid pack and the medication bag. "Go, go, go."

Oxana leads the way, marching briskly through the changing room, ignoring the half-naked figures who freeze with surprise at the sight of us, and into the wet-floored steam rooms. Here, again, everyone stares and no one moves. The choking heat makes my scalp run with sweat, and my glasses steam up so that I can't see where I'm going. Grabbing my arm, Oxana drags me into the cold plunge area, I wipe my glasses on my shirt, and there's the Pakhan, alone and naked, submerged up to his chest in the small marble pool. He has an impressive range of faded tattoos, including a knife through his neck, eight-pointed stars on his collarbones, and epaulets on his shoulders.

"Are you all right?" I ask him breathlessly. "We had a 112 call."

"I'm fine," the Pakhan says, smiling. "There's been some mistake."

He gapes at me, understanding neither the situation nor, probably, my shaky Russian. Oxana, meanwhile, drops everything she's carrying, and attends to the defibrillator.

"Our apologies," Oxana murmurs, and touches the defibrillator paddles to the surface of the water. The Pakhan shudders, his eyes widen, and he slips sideways onto his back, his legs trailing underwater. His face turns the color of putty, and his lips bluish-gray. His fingers twitch and grasp feebly at the water. His hands, I notice, are quite small for a man who has killed several people with an ax.

"Stand back," Oxana says, and gives him another jolt of electricity.

Still Dzabrati doesn't die. Instead he lies there open-mouthed, pillowed by water, staring at me sadly as if disappointed by my choice of wig. So I kneel, take Oxana's wrist with one hand to steady myself, and hold his head underwater with the other until the bubbles stop coming. It's nothing much. I don't even have to push very hard.

"Bit more?" I suggest.

I'm still kneeling there when, with a wet slap of plastic sandals, the two reception staff arrive. "I think he's had a heart attack," Oxana explains. "We're trying to get him out. Can you help?"

"I'm really sorry about the phone…" I begin, but Oxana is in an affectionate, almost light-headed mood. I'm wearing my black and yellow sweater under my leather jacket and she calls me pchelka, her bee. "You were so good," she says, slipping her arm through mine and dancing us down Moskovsky Avenue toward the Metro. "You really kept your shit together. I'm super-proud of you."

One of the men descends the ladder into the water, and between them they manhandle the Pakhan's naked body onto the tiled floor. As they do so Oxana discreetly reaches up and removes the micro camera from the top of the door frame. Kneeling beside the wet body of the Pakhan, I go through the motions of attempting cardiopulmonary resuscitation. To no one's surprise, it doesn't work.

An hour later, Oxana and I are walking away from the ambulance, which we've left outside Alfa Bank in Moskovskaya, where we found it. We're back in our own clothes. The ambulance service uniforms, the wigs and the medical equipment have been tossed into the back of one of the city's garbage trucks, and are now on their way to a landfill site.

"Yes. This week."

"Oh yes, so I do. OK, well… Can we talk about it this evening?"

"Hmm…" She half-turns. "Oh my goodness, look at that face. I'm teasing you."

"I love your fat."

"No, you have to trust me, remember?"

Her hand continues its exploration. I feel the tip of a finger probing my belly button. "Let's go back to the apartment."

Deciding that she's hungry, Oxana steers us into a half-empty McDonald's, where we order Happy Meals. "People think that there's this hard border between life and death," she says, cramming fries into her mouth. "But it's not like that at all. There's this whole area in between. It's fascinating."

"What is it?"

"Yes, we absolutely do."

I feel a hand slip under my sweater, and fingers tweaking my waist.

"That's not an answer. And stop pinching my fat."

I unwrap my burger. Our faces are inches apart. "Did Dasha say when she could get us the papers and the money?"

"So do we have a plan?"

"What about the rest of me?"

"Why not now?"

"Funny girl. So what shall we do?"

"You have to trust me, pchelka."

"You know why."

I take a bite of my burger. The greasy smell hangs in the air between us. "It's not really about me, though, is it? It's what we did in the banya that's making you want sex."

"Why?"

"So what is it that excites you about killing that nasty old fucker? I mean, it was pretty disgusting."

"Go on."

"This hamburger's pretty disgusting, pupsik, but sometimes that's exactly what you want. You can't live on beluga caviar."

"Honestly? It's both." She wipes her chin with a paper napkin.

"Killing people like the Pakhan makes me feel powerful. Konstantin always used to say: 'You're an instrument of destiny.' And I loved that. I love that I've changed history, and that if it wasn't for me the world would be a different place. Because in the end, that's what we all dream of doing, isn't it? Making a difference?"

Half a dozen blue-uniformed Politsiya officers swagger in, give a cursory glance around the restaurant, and start eyeing up the women at the serving counter. "Don't look at them," murmurs Oxana, surreptitiously sliding her hand from under my sweater, and I transfer my gaze to a copy of Izvestia that someone's left on the table. The lead story is about the upcoming New Year summit talks in Moscow between the Russian and U. S. presidents.

"Maybe. I hope so."

"Vy amerikanki?"

"They were just getting in out of the cold for a minute, and checking out the girls."

"Tourists," says Oxana in English. "Ne govorim po Russki." Her accent is comically awful.

The Politsiya officers mill around for a few minutes, attempt desultory banter with the female staff, pull out their phones and take selfies, and leave.

One of the cops saunters over. "Afternoon off work?" He's a mean-looking type with a bad shaving rash.

"Motherfucker," Oxana whispers. "We shouldn't have come in here. I think they bought the tourist story, but that could have ended badly. We've got to be more careful."

He nods and joins the others.

"What were they doing in here?" Oxana mutters. "What the fuck were they doing, taking those photos? Did you notice that they didn't get any food? Or even a drink?"

"You know what I'd really like to do?" I tell her. "I'd like to go into the city center. St. Petersburg has got to be one of the most beautiful cities in the world, and I've dreamed of visiting it for ages, especially in winter. The palaces, the art galleries… Just to walk down the streets, and see the frozen Neva river. It must be so magical."

"At the hotel. Four Seasons. Sozhaleyu. Sorry."

"British."

"Pasport?"

"I really and truly promise. But you have to promise me something too."

"OK."

"Say it. I promise…"

"You really and truly promise?"

"You have to trust me. I mean really trust me, despite the…"

"In winter, in the snow."

"Yes, in winter. In the snow."

"Promise me we'll come back one day, and explore it together. Promise me that."

"Don't be. Let's do what we should have done an hour ago, and go back to the apartment and have sex."

"I promise that we'll come back to St. Petersburg, and walk together by the Neva --"

"Yes, despite that. Even if things get really bad."

"What?"

"Psychopath thing?"

"Villa… Oxana, you're frightening me. What do you mean?"

"I know. I'd love to see it all too. And one day we will. But right now the center's too dangerous. There's mass-surveillance tech everywhere -- CCTV, facial recognition scanners, all that stuff -- and we have to assume the Twelve are monitoring it and have flags out for us. And that goes for every big city in the world. For now, we've got to stick to outlying areas."

"I'm scared now."

"I mean trust me. That's all."

"I always knew you'd do all of those things."

"How did you know? I mean, I was married, I had a husband, I'd never so much as looked at a woman…"

"Sleep with you. Have sex. Be your girlfriend."

"What's that about my tongue?"

"You, pchelka."

"Do it?"

"So what would you have done if I'd said no. If we'd run away together and all that and then I'd refused to do it."

"My silver-tongued girlfriend."

"That's true."

"You looked at me. And I looked back."

"And what did you see?"

"It's an English expression. It means you have a way with words. You know how to talk a woman into bed."