We are sitting around the curling tangerine skins and wine dregs at the end of yet another Christmas supper party, when the conversation turns - as it will in midwinter, after midnight and several bottles of Beaujolais - to ghost stories.

As usual, bursts of nervous, disbelieving laughter. Someone describes a television programme in which a poltergeist wreaked havoc on a radio alarm clock. "Define poltergeist," snaps one of the cynics.

More coffee is poured. Everyone vehemently agrees they'd never touch a ouija board.

Then an account executive called Carla bends her head to light a cigarette and says: "My house is haunted, actually."

"No!" we all shriek. Because it's just what we've been waiting for.

"It is," she laughs, her long blond hair wreathed in smoke, "I promise you. Cross my heart."

There are instant, mocking guffaws from a banker called Gus who - blindingly obviously - fancies Carla.

I have only just met her and we've barely exchanged two words, but already I know - mostly thanks to everyone else - that she's divorced and lives alone in Primrose Hill, that she can't have children, that she's writing a blockbuster in her spare time. ("A bonkbuster," Gus jumped to it when he heard. "No," she said crisply. "A blockbuster. For the money." Gus's eyes gleamed anyway.)

And now a haunted house. I both do and don't want to hear this story. Although I'm among friends, as Carla begins, the room seems to expand to three times its normal size, the area beyond the warm candlelight darkens, and I'm chilled by the idea of all that shadowy space above our heads - those silent, empty rooms.

I used to be terrified of ghosts. The house I grew up in was haunted, too, but only (in retrospect) by the constricting misery of my parents' marriage and, later, after our mother left, by our father's mean spirit and ruthless emotional power games.

On our weekend visits, he'd let my sisters and me (aged 12, 10 and 8) stay up and watch the late-night horror films and ghost stories on television - just as he allowed us all the fizzy pop and Mr Kipling cakes and sherbet dib-dabs we wanted.

In his house there were no rules and everything he offered we took. It was not done to spoil us, but to punish our mother. We were petrified of the films, yet could not resist them. It was hard to see why so many treats made us so unhappy.

In that house I heard ghostly footsteps up and down the stairs all night. In the morning, I lay and listened to the voices hissing through the heating system. I thought these were supernatural terrors, but I know now they were simply a means of calibrating my adolescent unease. Once I stared at a plastic horse on my bedroom mantelpiece and it fell over. Teenagers can make their unhappiness tangible if they try hard.

But, unlike Carrie, I grew up and got happy. It wasn't until I was 25 that I really saw a ghost. Sleeping alone in a girlfriend's south London flat (again, middle of winter), I woke in the night to see a small boy walking into the room.

Well, I barely saw him. What I saw was a short, wretched, formless human being whom I somehow perceived to be male, who entered the room and - apparently, as shocked as I was - drew back. I reached for the light. He had gone, but the air throbbed with his recent presence. I trembled for 10 minutes and slept all night with LBC on.

How do I know it wasn't a dream? I just do. I know what it's like when a dream wakes you and this was not it. This happened on the outside of me - which made it both easier and more difficult to deal with. I never told the friend. Not everyone wantsto live in a haunted house.

And now in the shadowy, tangerine-scented kitchen at one in the morning, Carla goes on with her story.

"So what's your ghost, then?" Gus lays his arm along the back of her chair. "Some hunk with his head under his arm?"

"Not at all." She does not look at him and I'm smugly glad to see she has his number. "It's a smell and a sound and a face."

These words inexplicably frighten me. Childish fears flood back. I look around the table. Everyone's waiting. Someone chuckles. "A smell?"

"Yes," she says, "A beautiful scent, rather like lilies, just wafting past now and again."

You'd think that would get a laugh, but it doesn't.

"And the sound?" someone asks.

"Little children." Carla holds her cigarette gently as if it were itself an exotic bloom. "Somewhere within the walls of the house. Kids laughing and playing, shouting - but always happy."

My hands are cold as ice. I can't say it, I can't ask it. But someone else does.

"And the face?"

She stubs out her cigarette, picks up her wine glass and swirls it. The liquid momentarily flushes the bulb red.

"Mine," she says. "At dusk, before I close the curtains, I see it pressing right up against the glass. Me. My own face just staring in at me."

Gus explodes - he thinks he has her now, "Your reflection!"

She gives him a pitying look. "No," is all she says.

And no one utters a word. Not even Gus. We're all staring at Carla's face. The fridge gives a little shudder. A long way away, someone coughs. More coffee is offered, but this party's over.