It was an evening shortly before Christmas. My wife and I were in Washington, D.C., too busy to cook, and so we decided to order out — Chinese food. We looked in the Yellow Pages, found the number for a rather dubious-sounding establishment on Connecticut Avenue, and called up to order the usual assortment of the exotic and the ordinary. The lady who took it all down said it would be delivered in 40 minutes, which made it about half past eight.

And sure enough, right on time, came the ring on the doorbell. There in the doorway stood a Chinese man with a plastic bag in each hand. There seemed nothing remarkable about him: he was plainly dressed, jeans and a leather jacket, unsmiling but pleasant in the way of all delivery men hoping for a decent tip. He lifted the bags onto the kitchen counter and offered up the bill, which was, I seem to remember, for 40-odd dollars.

There then followed a few moments of muttered fumbling as my wife and I patted our pockets and opened up wallets and purses and looked all around before concluding, to our considerable embarrassment, that neither of us had enough cash to pay the man. There were maybe 12 dollars in the flat, total. It wasn't a crisis, but it was a nuisance. Yet the man didn't seem unduly bothered: we lived in the center of the city, he said, and there were banks up and down the street below. "So I'll get my card," I told him, "and you and I will go down together and find a cash machine." He nodded. I found my coat, my wallet, told Setsuko I'd be back in a couple of minutes, and the delivery man and I left for the elevator.

As we waited for the elevator to come, I thought I might chat idly to him. Where was he from, I asked. "Shanghai," he said. I spoke a few phrases in my execrable Chinese, remarked on some places I knew back in Shanghai, and then told him — for no better reason than to make conversation, as the minutes dragged by — that I was writing a book, about a man named Joseph Needham.

He looked quite uninterested, of course. I looked at my feet, tapped my fingers on the elevator button. He whistled, tunelessly. Then something made me add Needham's Chinese name. "Yes," I said, "I am writing a book about Li Yue-se."

The delivery man suddenly turned to me, and he looked quite astonished. "Li Yue-se?" he asked, in a tone of stunned amazement. "Li Yue-se? Most wonderful man." Now he wouldn't stop talking: "Li Yue-se was a man who loved China. He is surely the most famous good Englishman ever to live in China. And you are writing a whole book about him? How wonderful for you! How wonderful!"

I was a little taken aback at the reaction, of course, but delighted. "Are you really interested?" I asked. "Would you like to see some books, some pictures?" And he nodded his head, vigorously. So I headed back to the flat, burst open the door. Setsuko looked dismayed; she had already set out the food neatly and was hardly expecting me to return with the restaurant delivery guy. I could sense that she was a little irritated, but I spent the next few minutes showing the man photographs — Needham in Xi'an, Needham in Cambridge, Needham and his mistress in Chongqing. And then, I said, there were copies of letters, diaries. Setsuko coughed. The rice was getting cold, she whispered. Then, into my ear, "Perhaps he's just being polite. Don't you think he'd just like his money?"

"Of course!" I exclaimed. And so the man and I left, and this time we managed to get into the elevator, the conversation became perfunctory once more, and we walked together to the bank machine. I got out the 40-odd dollars, paid him, gave him a tip, and then said an enthusiastic goodbye — happy to know there was at least one person in the city who knew who Joseph Needham was. Maybe he would be the first person to buy the book when it was published, I joked. And then I turned on my heel and began to walk back to the flat.

But after a few seconds I heard footsteps just behind me, and, Washington being the city it is, I glanced a little nervously over my shoulder to see who it might be. It was the delivery man, yet again. His car, or his bicycle, or whatever he had come with, was clearly parked near the doorway to our flat, and so it turned out that by coincidence we were walking together, bound for the same place, in a kind of lockstep. It was slightly awkward, considering I had just said my goodbyes. But I thought it would be rude to ignore him, and so I began the conversation once more.

"When you last lived in Shanghai," I asked, "what job did you have?" He replied, and this time in fair English, that he had worked in the computer department of the Standard Chartered Bank.

And I replied to him, since it was some small fact that I knew, with the single phrase "Macallee Bank." Standard Chartered in Shanghai had long been called Macaulay's Bank, and to old-timers, this peculiar name stuck.

"Yes," he said, and repeated the phrase: "Macallee Bank." And then something most peculiar happened. The delivery man stopped dead in the middle of the street, cocked his head on one side, and looked at me, strangely.

There was utter silence for half a minute, and finally he asked, his voice a little hoarse: "Simon?"

And in an instant there was a flash of realisation, a kind of lightning bolt. I said to him: "Gordon?"

For as it turned out, we knew one another.

Twenty years beforehand, I realised as we flung our arms around each other, I had made a film about this man, for the BBC. It was in 1987, I had filmed him, I had filmed his wife, and then as we stood there, hugging, I recalled that I had spent a week in and out of his tiny flat in the north of Shanghai, and I had brought him down to Hong Kong the following year and had made a second film about him there too.

This man was Gordon — Cui Guo-hong, I soon remembered was his Chinese name — and he'd lived in a fifth floor walk-up flat, dingy with coal dust; he'd ridden a bike, and his wife had worked in a factory, assembling radio sets. He was clever, but struggling — and, if he had ambition, he had somewhere to go.

And then, quite wonderfully, I soon remembered something else. In 1988 Gordon Cui had asked me if I would sponsor him to go off and study in the United States. I agreed to help. I suddenly remembered it all: I filled in the forms for him, I paid some fees, and, I further recalled, I paid something toward his first year's tuition at Drexel University, in Philadelphia. And so far as I knew he had gone off to America, and then, so far as I was concerned, had vanished into thin air.

Until this evening, almost two decades later. Here he was again, standing on Columbia Road in the Adams-Morgan district of Washington, D.C., far from Shanghai, far from Philadelphia, delivering Kung Pao chicken and white rice to our little flat on a Tuesday night in December. And I was the one who first brought him here. I was the reason he had come to America in the first place. Whatever success he had achieved, I had played some small but key part, all those years ago. And here, incredibly, he was. The connection was extraordinary. Of all the delivery men in all of the world, this one had to walk back into my life again: it seemed far, far beyond the believable.

Needless to say, Gordon came back upstairs with me, and we burst into the flat once more — me and the delivery man, back as friends again, a whole world away from where we had first met. And of course the reason that we rediscovered one another was because we had started talking outside the lift and he knew who Joseph Needham was. The most important good Englishman ever to have lived in China. Had we never talked about Needham, had he not reacted with such enthusiasm to Joseph's Chinese name, had I not asked him to come and look at the books — it is more than likely I would simply have gone down to the bank machine with him and handed him his money and said my goodbyes, and he would have walked off into the dark night and out of my life forever. But he didn't. He is now back in my life — in our life, once Setsuko recovered from the surprise of seeing him yet again — and in it forever, a fact that is a delight for all of us.

Oh. One final thing. In normal life Gordon Cui isn't, by the way, a delivery man. His PhD at Drexel University paid off handsomely, and he is a man with now a quite fascinating life and a future of infinite possibilities. But that is an entirely different story. Another time, perhaps.

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Simon Winchester's many books include The Professor and the Madman, The Map That Changed the World, Krakatoa, and A Crack in the Edge of the World. Each of these has been a New York Times bestseller and has appeared on numerous best and notable lists. Mr. Winchester was made Officer of the Order of the British Empire by Her Majesty the Queen in 2006. He lives in western Massachusetts.