It's six-thirty and Jacob and I are getting ready to go to an "ice spectacular" when the doorbell rings.

There's a girl - maybe nine or ten - pink nylon anorak too small, neck and wrists exposed, long blonde hair crinkling in the cold. She shivers - and falters into song: "We wish you a merry Christmas, we wish you a merry Christmas and a Happy New Year."

"Hold on," - as I speak, her voice (never exactly enthusiastic) trails off, eyes turn stony, "are you on your own?"

She stares at me, bored and sullen now, and a sad, spasmy shiver runs through her body, "No," - glancing twitchily behind her.

"Who's with you?"

"My Dad." She bites her lip.

"Where? Show me." We march down the path. Just around the corner, behind the dustbins, a man stands lighting a cigarette, hands cupped against the freezing wind. "Are you with her?"

"Yeah," - smoke escapes through his nose.

"You're her Dad?"

"Yeah." He's about 20. New leather jacket, tired face. I look at him, unsure of what to say next. He gives me a weary f--- you shrug, looks away. The child bites her nails suddenly and furiously, then he yanks her arm and they walk off.

I stand in the hall a moment, then, realising we're late, go up to Jacob's room to hurry him. But I find him sitting on his bed in tears. "Jacob, what is it?" - these are serious, trembly, held-in tears - "What's the matter?"

"Well," the sobs stop his breath, drown his voice, "you know how my kitten sometimes likes to jump up on the wash basin? Well, she had this bit of toothpaste on her fur," - and he cries, harder - "I just tried to trim it off and ... "

"Where is she?" I grab his shoulders, "Tell me now."

But the kitten is lying on the floor in the middle of a half-constructed Lego train track, batting the smallest bricks gently with her paws. There's a little, greyish bald patch on her side. I pick her up, check she isn't cut. Jacob throws himself on the bed again, sobbing. I take him in my arms, but he pulls away. "I just started snipping," he cries, "and I couldn't stop."

"You could have hurt her, you know that, don't you? She isn't a toy, she's your pet. You can break toys but not animals. You gave yourself a bit of a shock, didn't you?"

A look of pure pain crosses his face, "I'm so-o ashamed of myself."

We drive across London to the Albert Hall to see "Beauty and the Beast on Ice" - tickets courtesy of Auntie Mandy - a serious treat because it's way past Jacob's bedtime. The air's black and heavy with cold - fairy lights in shop windows, taxis pumping clouds of exhaust into the night. Jacob sits in silence - subdued excitement.

The Albert Hall's filled with women in mink coats and backswept blonde hair and young tourists with tired, East European eyes. The building's cold, draughty, oppressively smokey, the harsh brown bar brimming with angry people reaching over one another.

Waiting for the auditorium to open, we sit huddled together on the freezing lino steps. Jacob drinks half his orangeade and then feels sick. "How long will it take for her fur to grow back?" he asks gravely.

"A while," - I'm disinclined to lie to him about this.

"Every time I look at her, I'll remember what I did. She'll never forgive me."

I hug him, stroke his head, sniff his hot, schoolboy hair, "She's already forgiven you, she knows you didn't mean it and you won't do it again."

In the auditorium, music thumps from a speaker near our heads and we wait. Jacob suddenly climbs on to my knee - big and impossible and gangly at almost seven. Very soon he won't want to do this, I think, and pull him closer: all those limbs, that lively weight - the boy who one day won't allow himself to kiss me.

The Russian All-Stars skate on - blue satin costumes and bright, balletic smiles and flashing blades. Magnificent skating, histrionic gesturing, little plot. I feel Jacob's spine stiffen with excitement and then he sighs with pleasure. "The best show I've ever been to in my whole life," he pronounces at the first interval.

"Better than Power Rangers," at the second. Starving, we hunt the many bars for a sandwich, find an exhausted-looking egg mayonnaise bap, take a bite each and leave it.

The show comes down and we escape while they're still throwing bouquets. People stop and light cigarettes as they emerge and walk down the steps. The air buzzes with cold. "Did you ever do anything bad to Sparky?" Jacob asks me as we get into the car. Sparky was a Collie - the family pet of my childhood.

A sudden memory of another Christmas: Sparky, dashing through a snow- covered field, a trail of paw-holes behind her. Snow on her pointy nose, her dark widow's peak. Ecstatic barking.

"I can't remember anything in particular," I tell him. "But I'm sure I did, I've done lots of bad things in my life." In a quick, unbearable flash, the little-girl-on-the-doorstep's face comes back to me. The grey exhaustion in her eyes. I should have rung the police.

I squeeze Jacob's knee. He's thoughtful. Then, "I love you, Mummy," - this is something he says when life suddenly feels good or makes sense.

"I love you, too," I say, but I'm somewhere else. I'm in that long-ago frozen field with my sisters and our dog, laughter ricocheting - eery and forever - in that perfect snow lightness.