I sit upright, heart jumping. This is news to me. Despite everything, we’ve been looking forward to the disco for weeks.

‘What? Why?’

She doesn’t look at me. ‘My father.’

‘Well, I’m not going if you’re not.’

But I want to go. I don’t want to spend the evening at home with my mother, who sleeps nearly all the time, and my father, who’s distracted by a woman who works at the pub. I want to wear lip gloss and dance with my best friend, hide in dark corners and talk about boys.

‘Why don’t we sneak out? Remember that time we tried to go to the Radio 1 Roadshow?’ Sara is lying on Shannon’s bed and she’s lifting one leg and pointing her toe. ‘We didn’t get caught then.’

It’s an idle comment, a barely-even-thought-about comment. It was the first and last time we’d done anything like that, and we only got as far as the train station before we lost our nerve and came home again. For a minute, I think Shannon hasn’t heard, but then she glances at me, and it’s a look that changes everything. There’s excitement in it, a touch of defiance.

‘You could get ready here,’ she says. ‘Pamela leaves us alone when you’re here. We could pretend you’re staying the night.’

‘Can I stay the night?’ I don’t want to go home, to the smell of disease and disinfectant, and my father’s disapproval.

‘Stay the night, stay the night, stay the night.’ Sara flexes her ankle in time with her chanting, then rolls on her side, rests her chin in her palm and smiles at us.

‘Are you sure your parents won’t mind?’

Shannon’s face closes up. Sara’s is a mirror image. The atmosphere shifts. It’s swollen with sorrow and something I recognize as resignation, as if the sisters are to blame for the dark places they find themselves and there is nothing they can do about it.

‘They won’t care,’ says Shannon.

‘They don’t care about anything,’ says Sara.

‘Except what other people think of them,’ says Shannon.

‘They might give us money for pizza if you’re here,’ says Sara.

‘It’s safer when you stay,’ says Shannon. ‘Please stay.’

And what they say, in their matter-of-fact way, is horrifying but true.

I may not be a straight-A student but I’m not stupid. Or blind. Over the years we’ve lived next door to each other, I’ve played with the Carter sisters for hours and hours, and stayed the night at least half a dozen times. I’ve caught glimpses of the darkness that edges their lives, although the girls rarely talk of it.