When she had finished singing she clutched the collar of her coat and, giving a little bow as if in disdainful acknowledgement of the tremendous applause audible only to her, she took a violin from a cloth bag hanging on the arm of the wheelchair and began to play. Again, the sound was exquisite. Sibelius this time.
You get the picture: a beautiful blonde standing in the rain outside a jewellery shop at midnight. The cobbles glisten in the spill-over from spotlights illuminating the gold orbs on the top of a nearby baroque tower. She seems to encompass some great, tragic secret.
Her hand is trembling as she sings. Her voice and her playing have an unearthly clarity. Prague lends itself to such moments in a way a city like London never could. If different cities give rise to different ghosts, she was Prague's ideal ghost. And yet ... Something in me, some part of me I wished was not there, whispered, "It's stage-managed, it's not real," and I looked for the wires.
Late that night I was haunted by the scene I'd witnessed, and by my doubt as to its authenticity, and early the next morning revisited the spot the singer had stood. I tried to find out something about her from a waiter who was sweeping up outside a nearby bar, but it was impossible to communicate. Later the driver of a tourist horse and buggy told me yes, she was for real. He, too, had been mesmerised by her.
She had trained professionally, he said, but something had happened to her and now she was unemployable. I asked what had happened. The city was full of musicians, he said, and lots were drunks or addicts. And her? But he knew nothing else about her.
Standing listening in that little cobbled square that night I'd questioned the possibility of so much beauty and purity existing, and something inside me had all but died. The believer of fairy tales had drunk from the poisoned chalice of cynicism. It was just as well I went back to ask about her, otherwise I'd have been haunted forever.
Photographs of Prague give no real sense of the place. They simply cannot catch its essence. For example, one side of Prague's Old Town Square is dominated by the Church of Our Lady Before Tyn. In photographs the church looks impressive, but seeing it for real at night is another matter. At night Tyn - like much else - is illuminated and light bounces off the numerous steeples so that they seem to glow with a golden light.
All childhood images of what fairy-tale castles look like are represented by those spires of Tyn. It would have been easy to imagine people sitting inside the turrets spinning gold.
Across the Old Square from Tyn is one of Prague's main attractions: an astrological clock and calendar that, being built originally in the 15th century, puts the Earth at the centre of the universe. On the hour every hour, a door above the clock opens and Twelve Apostles peer out one after the other, while below them a skeleton (Death) pulls on a bell-rope and raises an hour glass. There are other figures on the clock tower, and on the face of a second dial in bright blues, reds and gold, are painted the sun and moon and signs of the zodiac.
Grand stuff perhaps, but the hawkers in the Old Town Square are immune to its beauty and they have developed the irritating habit of activating the voice mechanism of the toy chickens they are flogging the moment the skeleton raises its hourglass. At first I thought that maybe the chickens were really cocks, and the vendors were making them crow whenever a figure of Judas appeared - but no, nothing so sophisticated. For some obscure reason they've decided toy chickens are what tourists want.
Or could they be playing some kind of existential joke? After all, Prague is Franz Kafka's birthplace, the city he lived in all his life and where (and I find this more Kafkaesque than even his books) he enjoyed nothing better than a good game of tennis.
It's strange how, if you wander around the back streets of old European cities the cracked pavements, the crumbling masonry and paint flaking from buildings like snow, do not seem depressing sights at all. There's a romance about losing yourself in such backwaters, and I found this specially so in Prague. When the communists were in power, many of the narrow alley-ways that led to abandoned gardens and courtyards were left locked, and locals born during the regime were left puzzling as to what was down them. The little gateways have swung open now. In dusty, once stifling courtyards where plane-trees had been left to grow unchecked, people are busy lopping branches and repairing walls.
To the side of Charles Bridge - the original crossing over the River Vltava dating from 1357, and one of the city's most remarkable monuments - is Planterska Street, at the end of which is a small iron gate like one of the many mentioned above. It leads down under an archway and out on to a pontoon where rather decrepit rowing skiffs are tied up, waiting for hire.
Along the pontoon is a little floating cafe and I found few better places to sit, looking across the river to Prague Castle. No doubt better ones will be created, for over the years so much was left unused and locked away owing to bureaucratic inertia, much as to paranoia and the need to bully and control. After so many years of indifference Prague is healing itself, and is doing a wonderful job of it.
Of course the city is not solely about the past. The hotels and new restaurants (with what is surely Europe's worst food) are buzzing, and daily it seems a new bar or cafe has been opened, often by expatriates - a community dominated by young Americans and Irish, all of whom seem intent on recreating the Paris of Hemingway in the Prague of Havel.
If you have only experienced Europe through its western cities, or even through cities like Budapest or Krakow, then Prague will mesmerise.
British Airways (0345 222111) and British Midland (0345 554554) fly from Heathrow. BA's lowest fare is pounds 198 return, but you must travel before the end of this month. CSA Czech Airlines (0171-255 1898) flies from Heathrow, Stansted and Manchester. The lowest fare in September is pounds 219.40 from the London area, pounds 236.40 from Manchester.
You can travel by bus from London - a journey of around 18 hours - on Kingscourt Express (0181-673 7500) for pounds 85 return, daily except Monday.
For accommodation possibilities or more information: Czech Centre, 95 Great Portland Street, London W1N 5RA (0171-291 9920).