The train gets up speed. I don’t have a ticket. I don’t know where I’m heading. And I’m sure it’s obvious as I loiter near the luggage rack, sweating. I’d stick out less if I sat down in a seat. So I find somewhere quiet in a nearby carriage. There’s an old lady doing a crossword sat across the aisle. She looks like a safe person to speak to.

‘Excuse me,’ I say. ‘Is this the train for London?’

She nods. ‘Just one stop at Reading.’

I shut my eyes in relief.

We go through a tunnel that makes my ears pop, then over miles and miles of flat, flooded fields. Theo would love to be here right now. This window seat is perfect for playing ‘count the crows’.

First one to spot a hundred crows is the winner.

We’ve played it on so many journeys. It’s a Campbell family tradition. The winner gets the best flavour crisps from the multipack for lunch, which we all know are cheese and onion.

I don’t hear the carriage door open. When I look round there’s a man in a dark blue suit asking to see tickets. If I’m nice and polite he’ll let me buy one now, won’t he? I didn’t mean to get caught in the crowds. Reaching into my coat pocket, my hand freezes. An awful sinking feeling hits me.

Oh no. Please. No.

I check the other pocket. My purse was here! I double-check again. Check the other pocket. Check my bag.

The ticket man reaches me.

‘I need to buy a ticket.’ By now I’m hot to the tips of my ears. ‘But I can’t find my purse.’

‘Is that so?’ says the ticket man, like he’s heard the excuse hundreds of times.

I pat my pockets frantically as if it’ll make my purse reappear. The ticket man stares down at me. I take a gulp of air. This is all going wrong.

‘Look, I’m not a criminal,’ I say. ‘I’m just going to see my brother.’

‘Not without a ticket, you’re not.’

He says I have to get off at the next stop. There’s a fine to pay too. And he wants my name and address, though it’s got to go on a special form.

‘They’re at the front of the train,’ the man says. ‘You’d better come with me.’

I get up. People are looking at me now, which makes me go even redder. We walk down the aisle, through the sliding doors and into the next carriage. A few passengers glance up as we pass but I keep my eyes firmly on the ticket man’s back.

Then, as we go into another carriage, someone puts out a hand. The ticket man stops.

‘Yes, sir?’

‘Could you tell me which train …’

I don’t hear the rest. Just behind me on the other side of the doors is the toilet. There’s a sign on it saying ‘Out of order’. It’s my chance. I need to be brave. Tell myself I can do this, that getting to London is easier – far easier – than starting at a new school.

Any moment, the ticket inspector will stop talking and start walking again. It’s now or never. I take a step back. Then another. I’m through the sliding doors. The ticket man hasn’t even turned round.

Inside, the toilet stinks. There’s wet tissue all over the floor and the sink’s blocked. I lock the door quick. Within seconds, someone’s banging on it. I go very still. The handle wiggles.

‘You in there?’ says the ticket man.

I hold my breath.

It goes quiet. He must’ve gone. Lid down, I crouch on top of the loo seat. And wait. Near Reading the train starts to slow. It stops, the carriage doors open, and there’s thumping and rustling as luggage is put in the racks. Someone tries the door again. Then I hear the ticket man’s voice.

‘Well, she’s not in there now. She must’ve got off here and given us the slip.’

I just hope this means he’ll leave me alone.

The train judders. And then we’re away again.

Next stop London.

Not long to go. I try not to think of Nell. School will have phoned by now to say I’m absent and she’ll be fuming. And I bet she’s called Mum, who’ll be all stressed out. I get a stab of guilt. Mum doesn’t need anything extra to worry about. Perhaps this wasn’t such a brilliant idea.

Too late now. The train makes that clackedy-clack sound as we begin to slow down. Standing on the wet floor, I get ready to run.

The Tannoy comes on.

‘We are now approaching Paddington …’

I shift my bag onto my shoulder. The train squeals to a halt. I ease the toilet door open.

Out on the platform, everyone’s walking towards a barrier. A ticket barrier. I hesitate. Someone bumps into me.

‘Watch it, love,’ the person says.

At the barrier, the crowd thins into three lines. I join the longest because I need time to work out what to do. There must be a way to get through without a ticket. The queue shuffles forward.

I’m just four people away from the barrier now. The floor’s swept clean – no sign of any dropped tickets.

Three people away.

Two …

‘Got you!’

I’m jerked backwards. I try to turn round but the ticket man’s gripping my bag. He’s almost pulled me off my feet. Instinctively I lunge forward. Something rips. The ticket man still holds on to me. And then, quite suddenly, he lets go.

I don’t think: I run, scrambling over the ticket barrier like it’s life or death. Once I’m clear of the station, I slow down. The remains of my bag strap hangs off my left shoulder. There’s no bag attached; I suppose the ticket man’s still holding onto it.

If Lexie were here, we’d die laughing. But I’m on my own with no money, no phone and no idea how to reach the hospital. It’s not even remotely funny. Nor’s the fact that Theo’s card is still inside my bag. I’ve come all this way to give it to him, and now I can’t even do that.

To make things worse, it’s started to rain. A red bus goes by, then a taxi, then more taxis. Some have their lights on, which means they’re for hire – not that it’s any good to me. Stuffing my hands in my pockets, I walk faster. I don’t know if I’m going in the right direction but it makes me feel like I’m not giving up. After all, I’ve made it this far. I’m here in London. Theo can’t be far away.

At the end of the road, there’s one of those big maps of the area done for tourists. I’m so glad I want to throw my arms right round it; a bit of luck at last! Finding the ‘You Are Here’ dot, I then work out where the hospital is. It looks like a long walk down a straight main road.

A few turnings and I’m on that road. It’s noisy and smelly. Greasy-looking pigeons swoop around the traffic. Everywhere is grey: grey tarmac, grey buildings, grey sky. It looks strange after Darkling Wood, where everything is green or brown or blue.

At another of the tourist maps, I check my bearings. I’m still on track. The rain’s turned into that sharp, sleety stuff that stings your skin. But it doesn’t matter because it’s not far to go now and I can’t wait to see Mum and Theo’s faces when they see me. I get a fizz of excitement in my tummy. Or it might be nerves. Head down against the rain, I walk faster. The next turning should be it.