I knew we were somewhere in the French Concession, not far from the harbour, but otherwise I had lost my bearings. The chauffeur had for some time been steering us through tiny alleys quite unsuitable for a car, sounding his horn repeatedly to get pedestrians out of our way, and I had begun to feel ridiculous, like a man who has brought a horse into a house. But eventually the car stopped, and the driver, opening my door, pointed out the entrance to the Inn of Morning Happiness.

I was led inside by a thin Chinese man with one eye. What comes back to me today is an overall impression of low ceilings, dark damp wood and the usual smell of sewage. But the establishment seemed clean enough; at one point we stepped around three old women on their knees, diligently scrubbing the floorboards. Somewhere near the rear of the building, we came to a corridor with a long row of doors. I was reminded of stables, or even a prison, but these cubicles, it turned out, contained the inn's guests. The one-eyed man knocked on one of the doors, then opened it before any reply had been given.

I stepped into a small narrow space. There was no window, but the partitions did not go right up to the ceiling – the last foot or so being wire mesh – thus allowing light and air to circulate. For all that, the cubicle was stuffy and dark, and even when the afternoon sun broke brightly outside, it resulted only in the mesh throwing odd patterns over the floor. The figure lying on the bed appeared to be asleep, but then moved his legs when I took up a position in the gap between the bed and the wall. The one-eyed man mumbled something and vanished, the door closing behind him.

Former Inspector Kung looked to be little more than bones. The skin on his face and neck was shrivelled and spotted; his mouth hung open slackly; a bare, stick-like leg was protruding from the coarse blanket, though on his top half I saw he had on a surprisingly white undershirt. He did not at first make any attempt to sit up, and appeared only vaguely to register my presence. And yet he did not seem directly under the sway of opium or alcohol, and eventually, as I continued to state who I was and my purpose in coming to see him, he became more coherent, and began to show signs of courtesy.

‘I'm sorry, sir’ – his English, when it came, was fluent enough – ‘I have no tea.’ He began to mumble something in Mandarin, shuffling his legs about beneath his blanket. Then he appeared to remember himself again and said: ‘Please forgive me. I'm not well. But soon, I will recover my good health.’

‘I sincerely hope so,’ I said. ‘After all, you were one of the finest detectives ever to serve in the SMP.’

‘Really? How kind of you to say so, sir. Yes, perhaps I was a good officer once.’ With a sudden effort, he raised himself, and placed his bare feet gingerly down on to the floor. Perhaps out of modesty, perhaps because he was cold, he kept his blanket gathered around his middle. ‘But in the end,’ he went on, ‘this city defeats you. Every man betrays his friend. You trust someone, and he turns out to be in the pay of a gangster. The government are gangsters too. How is a detective to do his duty in a place like this? I might have a cigarette for you. Would you care for a cigarette?’

‘No, thank you. Sir, let me just say this. When I was a boy, I followed your exploits with great admiration.’

‘When you were a boy?’

‘Yes, sir. The boy next door and I’ – I gave a little laugh – ‘we used to play at being you. You were … you were our hero.’

‘Is that so?’ The old man shook his head and smiled. ‘Is that so indeed. Well then, I am all the more sorry I cannot offer you anything. No tea. No cigarette.’

‘Actually, sir, you may be able to offer me something much more important. I came to you today because I believe you may be able to provide a vital clue. In the spring of 1915, there was a case you investigated, a shooting incident in a restaurant called Wu Cheng Lou in Foochow Road. Three people died and several more were injured. You arrested the two men responsible. In the police records, the matter is referred to as the Wu Cheng Lou Shooting Incident. It's many years ago now, I realise, but Inspector Kung, I wonder if you remember this case?’

Behind me, from perhaps two or three rooms away, there came the sound of frantic coughing. Inspector Kung remained deep in thought, then said: ‘I remember the Wu Cheng Lou case very well. It was one of my more satisfying moments. I sometimes think about that case, even these days, lying here in this bed.’

‘Then perhaps you'll remember that you interrogated a suspect whom you subsequently established was unconnected with the shooting. According to the records, the man's name was Chiang Wei. You interrogated him concerning the Wu Cheng Lou, but he instead made some other quite unrelated confessions.’

Though his body remained a sagging sack of bones, the old detective's eyes were now full of life. ‘That's correct,’ he said. ‘He had nothing to do with the shooting. But he was afraid and he began to talk. He confessed everything. He confessed, I remember, to having been a member of a kidnapping gang some years earlier.’

‘Excellent, sir! That's just as it's recorded in the files. Now, Inspector Kung, this is very important. This man gave you some addresses. Addresses of houses the gang had used to hold their captives.’

Inspector Kung had been gazing at the flies buzzing around the wire mesh near the ceiling, but now his eyes turned slowly to where I was standing. ‘That is so,’ he said quietly. ‘But Mr Banks, we had all those houses checked thoroughly. The kidnappings he talked of were years in the past. We found nothing suspicious in those houses.’

‘I know, Inspector Kung, you would have done everything duty required of you most thoroughly. But of course, you were investigating the shooting. It would be perfectly natural if you didn't expend your energy on such a side issue. What I'm suggesting is that if powerful people had gone to some lengths to prevent you searching one of those houses, you would perhaps not have persisted.’

The old detective was deep in thought again. He said finally: ‘There was one house. I remember now. My men brought me reports. All the other houses, seven of them, I received reports. I remember it troubled me at the time. One last house, no report. My men were being prevented in some way. Yes, I remember wondering about it. A detective's nose. You will know what I mean, sir.’

‘And that remaining house. You never did see a report on it.’

‘Correct, sir. But as you say, it was not a great priority. You understand, the Wu Cheng Lou was a large matter. It had caused much outrage. The hunt for the killers had gone on for weeks.’

‘And I believe it had defeated two of your more senior colleagues.’

Inspector Kung smiled. ‘As I have said, it was a most satisfying moment in my career. I came on to the case when others had failed. The city was talking of nothing else. I was able after a few days to apprehend the killers.’

‘I read the records. I was filled with admiration.’

But now the old man was staring at me intently. Eventually he said slowly: ‘That house. The house my men failed to go to. That house. You are saying …?’

‘Yes. It's my belief that is where my parents are being held.’

‘I see.’ He fell silent for a time, digesting this colossal idea.

‘There's no question of negligence on your part,’ I said. ‘Let me say again, I read the reports with great admiration. Your men didn't get to the house because they were obstructed by persons in the higher echelons of the police force. People we now know were in the pay of criminal organisations.’

The coughing had started up again. Inspector Kung remained silent for a moment longer, then looked up at me again and said slowly: ‘You've come to ask me. You've come to ask if I can help you find this house.’

‘Unfortunately, the archives are in chaos. It's a disgrace how things have been run in this city. Papers have been misfiled, others lost altogether. In the end, I decided I'd do better if I came here to you. To ask you, unlikely though it is, if you remember. Something, anything about that house.’

‘That house. Let me try to remember.’ The old man closed his eyes in concentration, but then after a time, he shook his head. ‘The Wu Cheng Lou shooting. It is over twenty years ago. I am sorry. I can remember nothing about this house.’

‘Please try and remember something, sir. Do you recall even which district it was in? Whether for instance it was in the International Settlement?’

He thought for another moment, then shook his head again. ‘It is a long time ago. And my head, it doesn't work in a normal way. Sometimes I remember nothing, not even of the day before. But I shall try and remember. Perhaps tomorrow, perhaps the next day, I shall wake up and remember something. Mr Banks, I am so sorry. But just now, no, I remember nothing.’

It was evening by the time I returned to the International Settlement. I believe I spent an hour or so in my room, going through my notes once again, trying to put behind me the disappointment of my meeting with the old inspector. I did not go down to supper until after eight, when I took my usual corner table in that splendid dining room. I remember I did not have much of an appetite that evening, and was about to abandon my main course and return to my work when the waiter brought in Sarah's note.

I have it here now. It is no more than a scribble on unlined paper, the upper edge torn off. It is doubtful whether she gave the words much thought; it simply asks me to meet her at once on the half-landing between the third and fourth floors of the hotel. Looking at it again now, its connection with that small incident at Mr Tony Keswick's house a week previously seems all too obvious; that is to say, Sarah probably would not have written the note at all had it not been for what took place between us then. Oddly enough, though, when the waiter first presented it to me, I failed to make any such association, and I sat there for some moments, quite mystified as to why she should summon me in such a way.

I should say here that by this point I had run into her a further three times since the night at Lucky Chance House. On two of these occasions, we had seen each other only fleetingly in the presence of others, and little had passed between us. On the third occasion too – the night of the dinner at the home of Mr Keswick, the chairman of Jardine Matheson – I suppose we were again in a public place, and exchanged barely a word; yet, with hindsight, our encounter there could well be viewed as some sort of important turning point.

I had turned up a little late that evening, and by the time I was shown into Mr Keswick's vast conservatory, upwards of sixty guests were already taking their places at the several tables situated among the foliage and trailing vines. I spotted Sarah on the far side of the room – Sir Cecil was not present – but I could see she too was searching for her seat, and so made no attempt to approach her.

It appears to be a Shanghai custom at such events for guests, as soon as dessert has been served – even before they have had time properly to eat it – to abandon the original seating plan and mingle freely. No doubt then, it was in my mind that once this point came along, I might go over and exchange a few words with Sarah. However, when dessert finally appeared, I was unable to get away from the woman seated beside me, who wished to explain in some detail the political position in Indo-China. Then no sooner had I extricated myself from her than our host stood up to announce that the time had come for ‘the turns’. He proceeded to introduce the first performer – a willowy lady who, emerging from a table behind me, went to the front and began to recite an amusing poem, evidently composed by herself.

She was followed by a man who sang unaccompanied a few verses of Gilbert and Sullivan, and I surmised that the majority of those around me had come ready to perform. Guests went up one after another, sometimes in twos and threes; there were madrigals, comic routines. The tone was invariably frivolous, sometimes even bawdy.

Then a large red-faced man – a director of the Hong Kong and Shanghai Bank, I learnt later – made his way to the front wearing a kind of tunic over his dinner jacket, and began to read from a scroll a monologue satirising various aspects of Shanghai life. Almost all the references – to individuals, to the bathroom arrangements at particular clubs, to incidents that had occurred on recent paper chases – were entirely lost on me, but very quickly every section of the room became filled with laughter. At this point I looked around for Sarah, and saw her sitting over in a corner amidst a group of ladies, laughing as heartily as any of them. The woman beside her, who clearly had had a fair amount to drink, was roaring with almost indecent abandon.

The red-faced man's performance had been going for perhaps five minutes – during which time the level of hilarity seemed only to rise – when he delivered a particularly effective volley of three or four lines which set the room virtually howling. It was at this point that I happened to glance over once more to Sarah. At first the scene appeared much as it had before: there was Sarah, laughing helplessly amidst her companions. If I went on watching her for several more seconds, it was simply because I was rather surprised that after barely a year, she was already so intimate with Shanghai society to the extent that these obscure jokes could reduce her to such a state. And it was then, as I was gazing at her, pondering this point, that I suddenly realised she was not laughing at all; that she was not, as I had supposed, wiping away tears of laughter, but was in fact weeping. For a moment I went on staring at her, unable quite to credit my eyes. Then, as the uproar continued, I rose quietly and moved through the crowd. After a little manoeuvring, I found myself standing behind her, and now there was no further doubt. Amidst all the gaiety, Sarah was crying uncontrollably.

I had approached from behind, so that when I offered her my handkerchief, she gave a start. Then looking up at me, she fixed me – for perhaps as long as four or five seconds – with a searching gaze in which gratitude was mixed with something like a question. I inclined my head to read better her look, but then she had taken my handkerchief and turned back towards the red-faced man. And when the next burst of laughter seized the room, Sarah, too, with an impressive show of will, let out a laugh, even as she pressed the handkerchief to her eyes.

Conscious that I might draw unwanted attention to her, I then made my way back to my seat, and indeed, did not go near her again that evening other than to exchange rather formal goodnights with her in the entrance hall alongside the many other guests taking their leave of one another.

But I suppose, for a few days afterwards, I entertained a vague expectation of hearing something from her concerning what had occurred. It is, then, a measure of how much I had become engrossed in my investigations that by the time that note was brought to me in the dining room of the Cathay Hotel, I failed to make any connection with the earlier incident, and made my way up the grand staircase, wondering why it was she wished to see me.

What Sarah described as the ‘half-landing’ is in fact a substantial area strewn with armchairs, occasional tables and potted palms. In the morning particularly, with the great windows open and the ceiling fans whirring, I imagine it is a pleasant enough place for a guest to read a newspaper and take some coffee. At night, though, it has a rather abandoned atmosphere; perhaps owing to the shortages, there is no lighting other than that coming from the staircase, and whatever leaks in through the windows from the Bund down below. On that particular evening, the area was deserted aside from Sarah, whose figure I could see silhouetted against the huge panes, gazing out at the night sky. As I made my way towards her, I knocked into a chair, and the sound made her turn.

‘I thought there'd be a moon,’ she said. ‘But there isn't. There aren't even any shells being fired tonight.’

‘Yes. It's been quiet the last few nights.’

‘Cecil says the soldiers on both sides are exhausted for now.’

‘I dare say.’

‘Christopher, come over here. It's all right, I'm not going to do anything to you. But we have to talk more quietly.’

I moved closer till I was beside her. I could now see the Bund below, and the line of lights marking the waterfront promenade.

‘I've arranged everything,’ she said quietly. ‘It wasn't easy, but it's all done now.’

‘You've done what exactly?’

‘Everything. Papers, boats, everything. I can't stay here any more. I tried my best, and I'm so tired now. I'm going away.’

‘I see. And Cecil. Does he know of your intentions?’

‘It won't come entirely as a surprise to him. But I suppose it'll be a shock, all the same. Are you shocked, Christopher?’

‘No, not really. From what I'd observed, I could see something like this might be on the cards. But before you take such a drastic step, are you sure there aren't …?’

‘Oh, I've thought of everything there is to think about it. It's no good. Even if Cecil were willing to go back to England tomorrow. Besides, he's lost so much money here. He's determined not to leave until he's won it all back.’

‘I can see this trip out here's rather fallen short of your hopes. I'm sorry.’

‘It's hardly just the trip out here.’ She gave a laugh, then went quiet. After a moment she said: ‘I tried to love Cecil. I tried very hard. He's not a bad man. You probably think he is, the way you've seen him here. But that's not how he always was. And I realise a lot of it's to do with me. What he needed at this stage of his life was a good rest. But then I came along and he felt he had to do a little more. That was my fault. When we came out here, he did try at first, tried awfully hard. But it was beyond him, and I think that's what it was, that's what broke him. Perhaps once I've gone, he'll be able to pull himself together again.’

‘But where will you go? Will you return to England?’

‘Just now, there's not enough money to return. I'm going to Macao. Then after that, I shall have to see. Anything might happen then. In fact, that's why I wanted to talk with you. Christopher, I'll confess, I'm rather frightened. I don't want to go out there all by myself. I did wonder if you'd go with me.’

‘Do you mean go with you to Macao? Go with you tomorrow?’

‘Yes. Go with me to Macao tomorrow. We can decide after that where to go next. If you wanted to, we could just drift around the South China Sea for a while. Or we could go to South America, run away like thieves in the night. Wouldn't that be fun?’

I suppose I was surprised when I heard her utter these words; but what I remember now, overwhelming anything else, was an almost tangible sense of relief. Indeed, for a second or two I experienced the sort of giddiness one might when coming suddenly out into the light and fresh air after being trapped a long time in some dark chamber. It was as though this suggestion of hers – which for all I knew she had thrown out on an impulse – carried with it a huge authority, something that brought me a kind of dispensation I had never dared hope for.

Hardly had this feeling swept over me, however, than I suppose another part of me grew quickly alert to the possibility of this being some test she had set for me. For I remember that when I at last responded, it was to say:

‘The difficulty is my work here. I'll have to finish here first. After all, the whole world's on the brink of catastrophe. What would people think of me if I abandoned them all at this stage? Come to that, what would you think of me?’

‘Oh, Christopher, we're both as bad as each other. We've got to stop thinking like that. Otherwise there'll be nothing for either of us, just more of what we've had all these years. Just more loneliness, more days with nothing in our lives except some whatever-it-is telling us we haven't done enough yet. We have to put that all behind us now. Leave your work, Christopher. You've spent enough of your life already on all of that. Let's go away tomorrow, let's not waste a single day more, let's go before it's too late for us.’

‘Too late for what, exactly?’

‘Too late for … oh, I don't know. All I know is that I've wasted all these years looking for something, a sort of trophy I'd get only if I really, really did enough to deserve it. But I don't want it any more, I want something else now, something warm and sheltering, something I can turn to, regardless of what I do, regardless of who I become. Something that will just be there, always, like tomorrow's sky. That's what I want now, and I think it's what you should want too. But it will be too late soon. We'll become too set to change. If we don't take our chance now, another may never come for either of us. Christopher, what are you doing to that poor plant?’

Indeed, I realised I had been absent-mindedly stripping leaves off a palm standing next to us and depositing them on to the carpet.

‘I'm sorry’ – I let out a laugh – ‘rather destructive.’ Then I said: ‘Even if you're right, what you were saying just now, even then, it's not so easy for me. Because, you see, there's Jennifer.’

When I said this, a vivid image came back to me of the last time she and I had spoken, the time we had said our goodbyes in the pleasant little sitting room at the rear of her school, the sunshine of a gentle English spring afternoon falling across the oak-panelled walls. I suddenly remembered again her face as she first took in what I was saying, the thoughtful nod she gave as she thought it over, and then those quite unexpected words she came out with.

‘You see, there's Jennifer,’ I said again, aware that I was in danger of drifting off into a daydream. ‘Even now, she'll be waiting for me.’

‘But I've thought of that. I've thought about it all very carefully. I just know she and I can be friends. More than friends. The three of us, we could be, well, a little family, just like any other family. I've thought about it, Christopher, it could be wonderful for us all. We could send for her, as soon as we've settled on a plan. We might even go back to Europe, to Italy, say, and she could join us there. I know I could be a mother to her, Christopher, I'm sure I could.’

I went on thinking quietly for a moment, then said: ‘Very well.’

‘What do you mean, Christopher, “very well”?’

‘I mean, yes, I'll go with you. I'll go with you, we'll do as you say. Yes, you might be right. Jennifer, us, everything, it might turn out well.’

As soon as I said this, I could feel a massive weight lifting off me, so much so that I may well have let out a loud sigh. Sarah, meanwhile, had come another step closer, and for a second gazed deep into my face. I even thought she would kiss me, but she seemed to check herself at the last moment, and said instead:

‘Then listen. Listen carefully, we must do this correctly. Pack no more than one suitcase. And don't send on any trunks. There'll be some money waiting for us in Macao, so we can buy what we need there. I'll send someone to come and get you, a driver, tomorrow afternoon at half past three. I'll see to it he's someone to be trusted, but all the same, don't tell him anything you don't need to. He'll bring you to where I'll be waiting. Christopher, you look as if something heavy just hit you on the head. You're not going to let me down, are you?’

‘No, no. I'll be ready. Half past three tomorrow. Don't worry, I'll … I'll follow you anywhere, wherever you want to go in the world.’

Perhaps it was simply an impulse; perhaps it was the memory of how we had parted that night we had brought Sir Cecil back from the gaming house; in any case, I suddenly reached forward, grasped one of her hands in both of mine, and kissed it. After that, I believe I looked up, still clutching her hand, uncertain what to do next; it is even possible I let out an awkward giggle. In the end, she freed the hand gently and touched my cheek.

‘Thank you, Christopher,’ she said quietly. ‘Thank you for agreeing. Everything suddenly feels so different. But you'd better go now, before someone sees us here. Go on, off you go.’