103 Bayham Street, Camden Town was in a semi-bustling avenue one street over from the borough's main thoroughfare. There were semi-industrial buildings here rather than shop-fronts and street markets. Given the traffic, it would have been quicker to take the tube. But if I was to have Nari relaxed and happy, then a taxi we would take if that was what she wanted. Oddly, she fell somewhat silent inside the big London cab, her expression, staring out through the side window was not as cheerful as it had been when she got in.

"Is everything all right?" I asked, resting a single fingertip on the back of her wrist.

"What?" Nari jumped. "Oh yes, of course," she smiled brilliantly again, clear proof, if I needed more, that she was being less than truthful. Something was making Ms Kim despondent and it was nothing she felt in a mood to share. Naturally, I determined to discover what it was.

The cab stopped outside a long-windowed modernist structure with wide double-doors in the middle of the building. Above them, a vividly painted sign. Serpentynka, a name that conjured up the exotic and mysteriously foreign. Inside was an enormous cavern of a place, a vast warehouse-like edifice with at least three floors of furniture, sheer walls of artwork and, in the centre, an auction ring.

"You like the two chairs, yes?" I suspected Nari wanted to know where to begin.

"Yes, I want them," I nodded, peering around at the amazing collection of new, used and antique furniture, stacked up in a glorious confusion of narrow alleyways. Complete dining sets jostled for pride of place with rolls of old handwoven carpets; Victorian marble washstands vied with Swedish drinks trolleys. Suddenly, we reached the nirvana of period furniture-hunters; a space the size of a tennis court, covered, absolutely heaped, with Art Deco.

Not being an expert by any means, I was nevertheless able to recognise the bold arching lines, the geometric stepped shapes, the clean lines and dramatic sweeping elegance that framed the 1920s artistic ethos. There was something about the whole thing that resonated with me and I saw no reason to pretend otherwise. Nari grabbed my hand and all but dragged me towards a brilliantly glossy burled walnut dining table, its golden modernist style perfectly in keeping with the mood of my new apartment.

"This," she pointed dramatically. "This is perfect for your dining area," she was emphatic. "The colour is beautiful and neutral; natural wood will go with any style you eventually choose," she walked around the rectangular shape. "Plus this one expands in case you have a party or need an increase in working space for your ... work," she wriggled her fingers as if dismissing my 'work' as something best not discussed.

The table was indeed a beauty; the rich golden-red glow of the exquisitely-figured wood something I had not seen before. "How much?" I wanted to get a feel for how quickly I'd burn through Sir David's stockpile. The price card said £250 which, for an elegant object such as this seemed a steal. Nodding, I found it hard not to smile as Nari whipped out a notebook and started compiling a list of purchases. Within an hour, there was an entire page of carefully catalogued items, before she pointed me toward one of the interior cliff-faces decked out with all manner of art.

"What do you like, Mycroft?" for a moment, she sounded so plaintive that I frowned and turned, catching the same expression on her face I'd seen the previous evening. Reaching a decision and throwing most of my plans out of the window, I took the notebook from her hand and ripped out the filled page. Walking to a sales desk tenanted by three less than fully occupied sales personnel; I removed a wad of cash from my inner pocket, carefully counting out five thousand pounds which I set before their astonished gazes. I also laid down the page of recommended purchases each with a catalogue number noted in Nari's neat hand. Finally, I gave them my card, on the back of which I quickly wrote my new address.

"I'd like all of these things cleaned and shipped to this address by tomorrow lunchtime, please," I ignored their apparent bewilderment. "This should be sufficient payment for the moment, though if I am satisfied with the service of this establishment, I shall instruct my interior designer here," I bent my head towards Nari. "To return for future purchases." Waiting while a receipt was laboriously written out, I offered my confused companion an arm and walked her through the doors and around the corner to a quiet coffee shop I'd noted earlier. Sitting in a shaded corner, I organised tea and sandwiches, before I returned, clasping my fingers together as I leaned forward, capturing her gaze with my eyes.

"I know you're frightened," I began as gently as I could. "I know you are very worried about something and that the situation is eating at you inside," I looked deep into her suddenly widening eyes. "I want to help you but I cannot do anything unless I have a clear picture of the whole problem. Once I know the extent of the situation you are facing, I can offer alternative courses of action and help you decide what to do. Once you have decided what you want to do, I can help you do it."

Nari's eyes were saucer-wide as she sat, shocked into silence. I let her adjust in her own time as the tea and sandwiches arrived, pouring her a cup and placing it between her icy fingers.

"Have some tea and something to eat," I kept my voice low and soft so that she would relax, which she did in slow increments.

"Who are you?" she whispered, her stare never leaving my face. "Who do you work for?"

"Drink." I advised carefully and sipped my own tea. Sighing briefly, Nari did as I suggested, the hot liquid warming and easing the tension in her shoulders.

"How do you know these things?" she asked in a low voice. "Nobody knows this," she paused, shaking her head and hunting for words. "I need to know who you are working for or I cannot say anything." Realising that Nari's fear was less of getting into trouble and more of being discovered by the wrong people, I gave her a conspiratorial smile.

"I do not work for the people who want to hurt you," I said, watching her expression. No, that wasn't quite right. "The people who want to hurt your ... husband?" I tried, reaching out a hand to calm her again as she jerked back in shock. "It's all right, Nari," I spoke soothingly, bringing her hands back to hold the warm cup of tea. "Drink and you'll feel better. I'm here to help, not make things worse."

"You can't help," Nari shook her head again, clearly miserable. "Nobody can help."

"I think you might be surprised at what I can do," I risked a small touch to the back of her hand. "Please tell me why you are so frightened."

Nari sipped her tea for several long silent minutes. "Sir David is correct," she said, finally. "I am a spy, of sorts," she looked across the table at me and smiled wanly. "Though not a terribly good one, I'm afraid."

"A spy for the DPRK?" I asked softly.

She nodded. "It is all because I speak such good English, you see," she sounded heartbreakingly sad. "I said I would not, that they could not make me," she faltered into silence.

"But then they took your husband?" I asked, already knowing the answer. A standard, if rather brutal leverage tactic employed by just about every regime in the world. I hadn't made use of such a ploy yet, though realistically it was probably only a matter of time before I did, or at least the threat of such an action. Unfortunately, in the type of work I was learning how to do, the end often did justify the means.

Nari accepted my handkerchief as tears filled her eyes. "I am told to do terrible things," she whispered. "Awful things I do not want to do, but I must or he will die." I knew with a horrible awareness that her husband might be dead already, but it would be madness to cross that bridge before it arrived.

"What kind of things have you been instructed to do, Nari?" I kept my voice soft, not wanting to startle her into silence now that she appeared to be opening up. Wiping her eyes, she sipped her tea, calming herself .

"I am told to make friends with people in important positions," she spoke more normally. "People who are important politicians or who work in big government departments in Europe and London and Brussels," she added. "I am told to make friends with these people and listen to everything I hear when I am with them; to read their phone messages if I can or to trick them into embarrassing situations if possible."

"Is that what you were told to do with Sir David?" I heard my voice grow a fraction harder despite efforts to the contrary. "Have you been told to make friends with him? Good friends?" Nari nodded silently, hiding her eyes behind my white handkerchief.

"And me?" I asked. "Have you been specifically told to make friends with me?"

"Not by name," Nari blinked long lashes glistening with tears. "But anyone who works in Whitehall and who is important or powerful ..." she wept silently into my handkerchief.

"Do you know where your husband is being kept?" It would be a starting place, though not much of a one. I knew we had Korean and Chinese agents who regularly risked their lives and freedom to traverse unmapped woodlands and swift rivers into the darkest country in the world. It might be nothing, but it never hurt to ask.

"Somewhere around Wŏnsan, I think I heard it said," Nari sniffed and dried her eyes. Wŏnsan was a port city on the eastern coast, a busy naval base but also a place for summer tourism. Easier to reach by sea than land.

"If I am to be able to help you and possibly try and free your husband, I will need to have as much information from you as I can," I said, leaning forward again. "Are you willing to talk to one of my people and answer their questions?"

Frightened but lacking other options, Nari nodded. "But not in an office or those who watch me might become suspicious," she looked thoughtful. "I could go to your flat and talk to someone there?"

It wasn't the best alternative, but better than nothing. "It will be arranged," I said, allowing a smile to lift the sides of my mouth as the idea of her being watched sat uneasily in my gut. "But now you must be very brave and act as if we haven't had this conversation," I said, patting the back of her hand. "We should go back into the furniture place so that anyone keeping an eye on you will know that all is well. Are you game?"

"Yes." Breathing deep, Nari finished her tea, wiped her eyes and sat straighter, a faint smile once again shaping her mouth. Taking another long breath, she stood, brushed herself down and stepped around the table to take my hand, not my arm this time. If she was under surveillance, and I made a mental note to keep my eyes peeled for any sign of it, then our growing 'friendship' would be visible to all and sundry. Making our way back around the corner to Serpentynka, I walked us both back to the stash of deco furniture we'd been exploring earlier.

"I would like to buy the pair of leather chairs you showed me last night," I told her. "For my new office. I will need two other things and would value your advice," I paused, expectantly.

"Yes, yes of course," Nari looked up at me, eyebrows raised.

"I want a coffee table to go with the chairs and I want a single piece of art for the main wall opposite the desk," I said, lifting my gaze back to the three-story high wall of art works in front of us. "Something big and strong. Perhaps you could suggest something from here?" I waved my hand vaguely towards the mass of oils, acrylics and watercolours. "Something that would suit my mood."

"And what is your mood?" her natural optimism bubbling back up, Nari flashed a shy smile in my direction. "Something serious or something pretty?"
"Something suitable," I grinned, pointing her towards the furniture. "Go and find me a coffee table while I stand here and pretend to know something about art."

Throwing me a grateful smile, I watched as she moved to look at a collection of small tables. When I was sure she would be staying in sight, I turned to the enormous display of portraits and landscapes hanging up in the air. To be honest, I wasn't worried about a painting, but if it gave Nari an excuse to return to my flat for a talk ... Still staring at the confusion of paintings and ensuring nobody was in earshot, I pulled out my phone and called Bonneville. After explaining the situation, his response was direct. On no account was Nari Kim to be alone until she had been interrogated and debriefed.

I saw with some relief that she was still mulling over furniture and, by the expression on her face, she seemed a little less distraught than before. Folding my arms, I turned back to gaze upwards at the north face of Serpentynka's art mountain. Though I was no aesthete, there were colours and shades and images of things I found slightly pleasing and I craned my neck looking for something that might fit the bill.

"Mycroft, over here!" Nari waved as I turned, a pleased look on her face. Abandoning my art-search for the moment, I strolled over, keeping my hands in my trouser pockets as I'd been told this made me less intimidating. Following Nari's pointed finger, I saw a round coffee table no more than eighteen-inches in diameter. In beautifully inlaid timbers, the subtle hues of exquisite wood veneer described the stylised shape of a butterfly, its wings fully expanded to cover almost the entire circular surface, with each of its colours delicately accented by a different shade. There was also a patina of age that lay over the whole thing, rendering it special and unique. I would not have previously considered myself a lover of such goods, but I was discovering a hidden streak of appreciation for great style. Perhaps an interior designer's guidance was not the worst thing in the world to have.

"It needs a specialist clean," Nari lifted the little table up on top of a nearby larger table covered with a thick cloth. "Once the wood has been properly treated, you won't believe the colours and shades of the veneer," she looked up at me. "This is a lovely thing."

Yes, she was a lovely thing; I felt strangely uncomfortable at the situation in which Nari Kim found herself and how I espoused a system partly responsible for keeping her in it.

"It's beautiful," I nodded. "Please arrange for it to go to the appropriate restorer; you know far more about these things than I do."

Visibly delighted, Nari smiled knowingly. "In that case," she said, handing the table to me to carry, "you really do need to see this." She walked me a little way across the floor, before turning me around and pointing up at a moderately large painting hanging not ten feet away. My first impression was that it was filthy, but realising Nari wouldn't have pointed out anything unworthy, I stepped closer and tried to see beyond the grime and dust.

It was another butterfly, but whereas the one on the table was in shades of brown against a dark greenish-brown background, the painting was of a much larger creature, with outspread wings the shade and texture of woodland velvet resting against a background of faded sepia and old maps. Lustrous and elongated, the insect glowed beneath the painting's coat of dirt and old smoke, the fragile apex of each hindwing a curving symmetrical sweep of precision. It needed reframing and cleaning, of course, but with the right treatment, it would be perfect. I nodded, unsure for once of the right words.

"Then reach up and get it," Nari pulled an old chair into place, holding it still as I stepped up and unhooked the painting from its niche. Taking our purchases back to the same desk as before, there was only one man this time, an older fellow looking very pleased with life.

"I came by earlier," I said, handing the man another of my cards. "I apologise for any inconvenience, but I'd like both of these items added to the list of purchases, though we'd prefer to take these with us today." Upon reading my name on the card, the man's smile became positively sunny as he saw I had returned for more.

"Of course, Mr Holmes," he beamed. "Would you like me to have them wrapped for you, or shall I have them taken out to your car? The boys are already working on your earlier order and we'll have everything out to you by lunchtime tomorrow as requested."

Carrying the little table and the old painting, Nari and I once again made our way out onto the street. Knowing now that she was probably being watched, that perhaps we both were being watched, I kept a careful lookout for anything odd, but sensed nothing untoward. If anyone was watching, they were very good at it.

###

I had the cabbie wait outside the restorer's studio as I lugged and Nari took the lead. Both the table and the painting could be cleaned, restored in the few places of slight damage and returned to new. It would take about a week in total, as the required work wasn't that major. Leaving a cash deposit and another of my cards, the next stop was my soon-to-be-home in Pall Mall. Going up in the lift this third time was no less thrilling than before, though at least this time I felt slightly more adult about the sensation. Unlocking my very own front door made me realise, somewhat ruefully, that the first official use of my flat was to be one of espionage. Apparently, not even my more private joys were above the shadow of my work.

It was immediately obvious that someone had been here in my absence as there was now a minor mis-en-scène in the living room area: a cheap table and several ordinary chairs had been set up for a very specific and all-too obvious purpose. As soon as Nari came into the flat, her eyes grew wide and she stopped dead, painfully aware I was about to ask her to do something she had been doing her level best to avoid.

Her face had paled and there was a place just above her jaw where a tiny muscle flickered. Needing to take her away from these thoughts. I reached down and took her hand. Tugging gently, I pulled her towards the front of the apartment where the walls of sheer, heavy glass let in the afternoon light.

"Tell me what I should have in here," I said, bringing her into the master bedroom and holding her hand through my arm in as casual a way as I could. A relatively large space, I only knew I needed the basics; a bed, somewhere to hang my few expensive suits and perhaps a chest of drawers to house the endless supply of socks my mother believed I needed. Momentarily distracted, Nari stared at the wall that reached beyond the ensuite bathroom.

"What's behind there?" she said, pointing. The far side of the wall was home to a tall cupboard at the end of the hall and which used to hold the old hot water tank. "Because if you could put a door in there," Nari indicated a spot about three feet to the left of the ensuite door. "You could make yourself a walk-in wardrobe which means you wouldn't need to buy a large, free-standing piece of furniture and which would then open up the space in here to be more creative with the remainder of your pieces," she added, raising her eyebrows at me. As I probably wouldn't have considered this until after I'd moved in, I nodded in appreciation. It was a clever move and I would see about getting it done.

The small phone she kept in her bag started to ring and she looked at me apologetically as she moved away to take the call. To give her privacy, I stepped out of the bedroom to examine the actual size of the hall cupboard and estimate how much additional room I might access if I followed Nari's ingenious plan.

I heard swift footsteps and the opening of the front door. Stepping back into the hall, I saw the door was hanging open and I broke into a run. If Nari was making a run for it, then the phone call had probably been the cause. I scowled; despite my job, I had no wish for her to be more distressed than she was.

The lift wasn't in operation, so she had taken the wide marble staircase, a perilous escape in heeled shoes. I followed, able to take steps two at a time, unencumbered by any such problem. I caught up with her as she pulled open the unlocked front door, dashing out onto the pavement, stopping short as she almost ran into Bonneville himself.

Sir David looked at her speculatively as he closed the rear passenger door of his car, his eyes lifting to me as I barrelled out of the door immediately behind her.

"Problem?" he asked, his gaze moving between us.

"Please! I have to go ... I cannot stay here with you!" Nari's voice was strained and frightened, her bag slipping from her shoulder to the ground as she turned backwards and forwards, seeking a way out.

"Nari ..." I held out the small, though surprisingly weighty bag. "Sir David and I are here to help you but we need to know as much as you can tell us about your husband's situation before we can do anything," I despised myself as I said the words knowing in all likelihood it was already too late for help. "Please come back inside and sit down. You're overwrought and upset. Please come back inside." Bonneville remained silent, observing but not yet participating in the unfolding drama.

As if her strings had suddenly been cut, Nari drooped, sighing heavily. Nodding almost imperceptibly, she took her bag and re-entered the building. Sir David remained silent, handing me a carrier bag filled, I suspected, with the makings of tea. We walked to the lift in silence.

"Why don't you sit down and I'll make some tea," I strode into the kitchen feeling wretched. Unpacking the tiny kettle, paper cups and other essential ingredients of the British panacea I hoped that, with luck, Nari's longer relationship with Sir David might be useful. I doubted my involvement would be much help at this point but listened to the sound of soft voices as I returned clutching paper cups of steaming tea. It wasn't the elegant daily little ritual I'd come to appreciate in Bonneville's office, but it would do.

As I approached the table, I saw Nari slide her phone back into her opened bag. As I placed a paper cup in front of both she and Sir David, she jumped nervously, knocking the bag to the floor once again.

"I shall have to buy you one you can wear messenger-style," I smiled carefully as I lifted the bag back up to the table, nodding to Bonneville as I did. His eyes flicked to the third empty chair; clearly he wanted me involved. I headed back to the kitchen to collect my own cup of tea; it might only be a prop in the forthcoming discussion but I was learning the value of props, even one so humble as a paper cup.

It was only as I held the flimsy container in my hand that I realised something was wrong with Nari's bag. It had been noticeably heavy when I retrieved it from the pavement and, even though I had seen her drop her phone back inside, it had still been lighter when I picked it up the second time. Not a great deal lighter, but still a significant difference. This suggested she had removed something from the bag when she returned the phone, but I had seen her hand and there had been nothing immediately visible. Which meant whatever she had taken from her handbag was small but disproportionately heavy for its size ... not a pen, not a comb, but something sufficiently long and thin to be hidden in her small hand.

Long and thin and heavy ...

Dropping the tea, I flew back into the living area of the flat. "Watch out, she's got a knife!" I shouted, reaching out for Nari, even as she came to her feet; a shining flick knife suddenly visible in her fingers.

"I told you to let me go!" she screamed, taking a step closer to Sir David who was already rising to his feet. He could not move swiftly enough to avoid the downward thrust of Nari's hand which had reached the apex of its swing and was beginning its deadly descent. I acted without conscious thought, throwing myself between Sir David's body and the glittering knife.

The pain of being stabbed is infinitely strange. There is the frightening thud of impact, immediately followed by the ghastly sensation of one's flesh being cut; instant messages of pain flashed throughout the body by offended nerves. I felt myself falling to the floor, too shocked at the knowledge I'd actually been stabbed to concern myself over the details of the matter. The only thought I recall with any real clarity was that I'd need a new waistcoat as the blade had gone clean through this one. I didn't even feel the floor when I landed, my eyes tracking static table legs and the slow-motion movement of the human variety. There were noises ... sounds, I am certain, though of what or made by whom, I could not say. I closed my eyes as consciousness faded.

###

The hospital doctor told me I was fortunate. Had the knife been a half-inch higher, I would have been skewered through the heart but as it was, my rib took the brunt of the blow, a small chip showing up in the X-ray. There had been a fair bit of blood, but the actual wound was relatively small, requiring no more than eight stitches with the promise that the scar would be barely noticeable.

Bonneville had, of course, insisted on my recovering fully in a private clinic. My wound was sore rather than painful and within a day of bed-rest I was bored to tears. Accepting my word I would not overdo things if I were to return to my flat, Sir David delivered my keys and an embarrassed apology.

"Most unfortunate situation," he said, looking sombre. "All dealt with now, of course. Turns out Ms Kim's watchers had grown suspicious of her recent movements and decided her usefulness to them was at its end. They wanted to ensure she'd be taken care of by us, one way or another," Bonneville sniffed, his indignation plain.

"Is she alright?" I asked, feeling the pull of the stitches as I stood properly upright for the first time in two days.

"Deported back to South Korea," Bonneville frowned heavily. "Though I doubt the South Koreans will want anything to do with her either."

Poor Nari. Used as a pawn by all sides. I was disgusted with myself.

###

My refusal to press charges helped, I think. Nari had been arrested as soon as she got off the place in Seoul, but there was little anyone could do if no official complaint was made. Likewise, there was no record anywhere of her more ... covert activities in Britain. Let the Korean authorities think what they liked; at least I knew I was not responsible for making her situation any worse.

I was working from home in my new office several days later, when Bonneville's recently-installed concierge, a retired MI5 employee, called on the internal phone; a package awaited in the foyer. Dropping what I was doing, I tried to remember what else I was expecting; Sir David having arranged things in my flat, as well as having all my personal stuff packed up and brought over from the apartment in Carlton Gardens.

There were actually two packages; one, a box about two-foot square and the second, obviously a painting. Carrying them back up in the lift, I returned to my office where the two leather chairs Nari had sold me held pride of place in one corner. Carefully, I opened the box and pulled the small table out from within its nest of crushed newspaper.

The butterfly glowed. A beautiful gift of a thing; elegant, charming and immensely stylish. The table slotted between the chairs and looked as if it had been made for them. I snipped the cord binding the painting's wrappings and carefully pulled the several layers of white paper away from the newly-restored finish.

Oh god. It was a lovely thing. I had no idea who the artist was, but the lustrous work was incredible and I knew I'd never see the like again. I leaned it across one of the chairs, reminding myself to organise its proper installation. It deserved no less than the best. I wished Nari could have seen it but she had dropped out of circulation and now nobody could tell me where she was. Staring at the glowing butterfly was a bittersweet experience of beauty and infinite sadness.

I sighed bleakly and returned to my work.