So when do we first know something is wrong?
Is it the day he gets up late for his maths GCSE - so unlike him - and rings his father to say he hasn't got a ruler and what should he do? And doesn't seem to care that going to buy one will make him late.
What's wrong with him? his father says later, bafflement and hurt in his voice. He almost missed the exam. He wasn't even slightly prepared. All these years of working and suddenly he's happy to throw it all away?
Or is it the day we are moving house - moving to a bigger, more rambling house with a great big basement music room for him to play his songs in - and he refuses to join in the excitement? He barely manages to pack up his own room, his own things - and then there finally comes a point where there's nothing left to move from the room but his bed. With him in it.
The removal men are embarrassed.
Look, mate, we can't just tip him out.
Oh yes we can.
We tip him out. We do. We try to make light of it.
That's teenagers for you, eh? one of the men says. You should see my son. You should see his room.
I smile, but I know he's just being kind. This isn't like that. By now we aren't like other people. Our child's eyes are furious, black.
For God's sake, he growls, what's the matter with you? Can't you see I'm trying to sleep?
But, darling, we're moving house.
Does it really have to be right now, this minute?
Well yes, it does. The removal men are here and the van is packed -
That's right, just organise everything to fucking well suit yourselves!
When we tell the story later, people laugh. Typical bloody teenager, they say. Sleeping in. Not lifting a finger to help.
We try to laugh too.
Is it possible, we ask ourselves hopefully, that they're right? That he's only doing what other kids do, that we're overreacting? How we'd love that to be true. But in our hearts we know what's true. All over the city, even in our own street, other families aren't living like this.
Because there are other things. Cash going missing. Tantrums that seem to come out of nowhere and be about nothing, but which destroy everyone's mood, leaving misery in their wake.
Threats of sudden and uncharacteristic violence. The day when, for no reason I can really explain to myself, I begin hiding all the sharp kitchen knives under the old boxes in the cupboard under the stairs.
His seeming inability to stick to any plan - our child who has always been so reliable, so easy to deal with, so very considerate and sensible. Our child who would phone if he was going to be three seconds late.
Now, his complete inability (unwillingness?) to get to school on time. Followed by his inability (unwillingness) to get to school at all.
But you don't panic. You are a good parent, a happy, loving fire-fighter, ready to deal with anything. So what do you do? You cope. You cram your work into a small space so you have more time for him. You cancel social engagements.
You try to talk to him. You stay cheerful. You look for the good things. You hope this is just a terrible phase. You wait for him to turn a corner, for things to change.
But you still hide the knives. You keep your handbag with you.
A good morning is a morning when no one shouts or cries, when life plods along. And there's one memorable dark winter's morning when life suddenly feels good again, because he gets up on his own, gets dressed and comes down and eats an egg you've cooked.
Is this it? Is this the corner?
But then there's another morning when you let the same hope bloom only to have it dashed.
Can you believe it? I tell his father, he actually got up when I woke him, came down, had breakfast quite happily, then suddenly for no reason at all his mood seemed to collapse. He told me he couldn't go in for the first lesson. And he went back to bed.
Suddenly for no reason at all. It's what we say all the time these days.
So I go up there. I put on the light and sit on the edge of his mattress and I touch his curly head. I put my hand on his waist, his shoulder. He's taken off his jeans but kept on his T-shirt and jumper and pants.
What's going on? I say softly. Tell me what's the matter.
Go 'way, I'm trying to sleep.
Darling, you can't do this.
I can do what I fucking well want to do.
But - it makes no sense.
(He says nothing.)
Do you see, it makes no sense?
(Silence.)
You did the hard bit already. You got up. You had breakfast. What's stopping you going in to school?
Gotta sleep. Go 'way.
You can't be late again. Do you realise how many late days you've had in the last two weeks?
Doesn't matter. I'll go in later.
(A sigh.) You promise? Promise you'll go in?
Yeah, now go away.
I go downstairs. Try to work. At lunchtime he's still fast asleep. He doesn't go in.
His father sits in the kitchen with his head in his hands.
There's a name for this, he says, it's school refusal. They call it school refusal.
And we look at each other almost hopefully, as if the discovery of a label might shed some light.
Two days of this and then he goes in.
He goes to school but doesn't come home. At almost midnight he bangs through the door, gripping the walls to steady himself My God, are you OK? Are you drunk?
He blinks at me. He doesn't quite seem drunk. His face is grey.
Are you all right? Where have you been?
When he speaks, his voice is strange. He makes no sense.
Speak to me, his father says. What have you done? You've taken something. What have you taken?
He tells us to fuck off and leave him alone. We follow him up to his room. It's dark. I put on a light. His eyes look through me. A small stream of something comes out of his mouth. Not quite vomit.
Quick, says his father. A towel. He's being sick.
But it's not like sick. Green water.
Should we call an ambulance? We decide not. We decide to let him sleep and to check on him. At 2 a.m. I check on him and find him asleep, his cat hunched on the bed next to him. The bedclothes are wet.
Next morning he's fine. We tell him he's not to go out on school nights. Not while he's still at school.
I'll do what I see fit, he says.
We can't go on like this, his father says. I just can't do it. I can't live like this.
A friend tells me her son can't decide whether to apply to Oxbridge or have a gap year first. I find it hard to have an opinion. Another friend tells me they had a great sixth form all lined up for their daughter, but she's gone and got a scholarship to this performing arts school- she's passionate about drama. What on earth should they do? As problems go, it's not a bad one, I say, trying to sound amused, rather than uninterested.
Meanwhile at home things are unravelling both slowly and fast.
It all happened so slowly. And yet it was amazing how fast it all unravelled.
So, it's a cold and bright February morning and, though I frequently tell myself that it could have been either of us, it isn't his father, it's me. I'm the one who tells him to go. His mother. The one who carried him and loved him and felt him move and grow. The one whose skin stretched once a long time ago to make room for him. She's the one who decides it would actually be preferable to live without him.
Though people might imagine it the other way round, it isn't his father but his mother who snaps first.
This fact is still surprising to me. No, surprising isn't quite the word. It knocks me out when I think of it. It makes me want to die. It knocks me to the ground. Where did I find it in myself to tell him to go?
May be I find the strength because it's no longer just about him.
That morning I discover that he's been giving his thirteen year-old brother drugs. He and his friends - selling him cannabis. Teaching him to roll a joint when he still occasionally plays with Lego and listens to story tapes at night.
I did notice my youngest's appetite and energy fluctuations and his increasingly frequent bad moods, the way he'd rush for the Weetabix as soon as he got in from school. I'd started to worry about him. Should he have a blood test? Thinking his eyes looked rather pink, I took him to the doctor. Might he have conjunctivitis?
Later our boy tells me how much they all laughed about this, he and his friends. They thought it was the biggest joke, the conjunctivitis thing. Remembering this now makes me strong.
I don't actually throw him out. This is important, because later he will say I did - he will insist this is what happened. But I don't. Instead I do the next best thing. I give him a clear ultimatum.
Behave yourself and live in this family properly and decently, or go. Get up and go to school, or go. Go to bed at night, or go. Stop causing misery and chaos everywhere in this home, or go. Stop giving your brother and sister drugs (most of all, please, whatever else you do, stop doing that), or go. Stop stealing from us and threatening us, or go.
We cannot continue to live with you if you do all of these things.
What do I imagine? That he'll turn around and agree to change, to stay in, to give up drugs, to do all of those things? I don't think so. We've spent so many months I've lost count, may be more than a year, talking to him, coaxing him, begging him. We've drawn up contracts, offered incentives, offered help. We've cried, we've laughed, we've told him how much we love him. We've reminded him of what life used to be like before all of this.
But nothing has changed. Or at least, something has changed - the family itself has changed. It's no longer what it was - a place of safety and happiness. It's started to come undone.
Some days we blame each other and some days we blame ourselves but mostly we just sit there and feel quietly hopeless. Someone once told me that a definition of stress is responsibility without power and that's exactly what this feels like. We feel so completely responsible and we love our child so much, and yet we have no power to act. What can we do? How can we possibly act, when the only act that will mean anything, the only one that will have any effect, is to force him from our home?
His younger brother and sister seem to know this. I feel them watching us, waiting for us to take control. I cannot bear the look on their faces. No family should have to live like this.
And it's a cold February morning, the day of one of his AS mock exams which he's just tried and failed - or tried and refused - to get up for. It's a cold February morning, the air punishingly white and sharp, when I finally say it.
This is it. This is the end. I mean it. Behave or leave.
I say it and then I walk away. I go downstairs and stand for a moment in our bedroom with my heart thumping. And something, I don't know what, makes me cross over to the window and look out and there's a big old-fashioned funeral going on down in the churchyard below. Black-clothed people, black horses with great fat black plumes, the whole lot, stamping feet, their breath in clouds. And I think, What have I done? What have I just said? And then I think something else: I think, This moment will pass. Just like everything else. It will pass.
And he goes. Surprisingly easily, it turns out. That's all it takes. I can't remember the door closing or what happens next. I can't remember much at all about what I feel on that day but I know that relief is part of it. No more hiding my handbag, no more locking my study, even if I only want to make a quick cup of tea. No more taking a breath when I hear him on the stairs, wondering which member of the family I'm going to have to protect from which aspect of his behaviour next.
The world looks different. Calm, clean, shiny with possibility. Suddenly it's actually worth wiping down the kitchen counters, getting the cupboards straight, turning lights off at night. It's worth it because they'll stay that way. The way we leave it will be the way we find it. It's even worth cooking a meal, because everyone will sit down happily around the table to eat it.
It's amazing to be able to go to bed and not come down in the night to turn off lights and check the front door isn't open, or that the ring on the cooker hasn't been left on.
His brother and sister seem strangely young. They start being silly again, laughing at their father's jokes, which is something they haven't done in ages. There's a new lightness in the family. We'd all forgotten what normal daily life was like. Slowly, happily, we relax.
Our child is gone and we can all relax. A lifetime of loving him and taking care of him and now he's out there somewhere on the streets and we can all relax.
The idea is terrible to me.
That first night, his cat creeps into our room and - for the first time ever - sleeps on the bed with me. His black cat - the small black kitten with a white bib that we gave him for his sixth birthday, the cat he called Kitty because, after going through a zillion other possible names, he really did think Kitty was the best one. I curl my arm around her and I sleep too, even though my heart is hollowed out, blackened and burnt.
All of this happens just a few days after his seventeenth birthday.
Things happen. Something can happen. You're just getting used to the world and then it vanishes. Or, you love a person and expect to have them close by you for ever and then they go. Your life, your child, the world. It vanishes. It falls away. And the life you thought you knew, the one you were so certain you could count on, it suddenly isn't there any more and, before you know what's happening, the level ground you were standing on, it slopes and then it tips - and then what?
I miss my boy so much.
And something about Mary Yelloly, something about you, the loss of you, has gripped me. I'm thinking about my boy almost all the time now, yet even so, I find myself so moved by you. The loss of you.
Mary.
Cool fingers touching my sleeve. Who are you? Are you there? Who were you?
I wonder what's left of you.
If someone lives on this earth for just twenty-one years that's just four years longer than my boy - and then they go, well, what's left? What do they leave?