I reply, ‘No,’ so quickly that Mam blinks in surprise. ‘I … I mean, not tonight, Mam.’ I force a little yawn, but I can tell Mam’s a bit hurt. She likes reading us stories, even if it’s Kobi the Cave Boy for the billionth time.

‘I’m working lates a lot this month,’ she says. ‘There may not be as many chances.’

I certainly know the thing by heart, and at least it’s not long. Seb reaches under his bed and pulls out the very well-used picture book. I always thought he’d grow out of it, but he never did. I can’t even remember a time when he wasn’t obsessed with it.

Mam settles down on Seb’s bed and begins reading, and Seb mouths along with the words, while I stare at the Dreaminators, silently urging her to speed up.

‘In the shadows of the cave, the fire flickers red,

And Kobi lies down with a rock beneath his head …’

It’s the story of a boy in the Stone Age who lives with his family in a cave, long before houses and cars and aeroplanes and machines and clothes were invented. There’s a lake, and another tribe of Stone Age people, and he rides on a mammoth …

I yawn again, a big one this time, and Mam pauses.

‘Aww, I want the end,’ says Seb, but I manage to catch his eye and I flick a glance upwards. He gets it. ‘But if Malky’s tired that’s okay.’

Mam closes the book and looks between us, with mock surprise. ‘Hang on – have you two just agreed on something without arguing?’ She runs her fingers through her short curls and shakes her head. ‘I hope it lasts! Sweet dreams,’ she says. She always says that: it’s like an unreliable magic spell that only sometimes works. Then she switches the light off and the twin circles of dull blue light hanging over our beds stand out in the dark.

‘Do they stay on all night?’ she says. Then, before I can answer, she starts to sniff the air. ‘What’s that smell?’

‘Yeah – I noticed that as well,’ says Seb. ‘I thought it was Malky’s socks!’

It’s rancid yak’s butter, but obviously I’m not going to say that. Instead, I say, ‘Dunno. I can’t smell anything.’ Mam shrugs and goes out.

We lie awake in silence for a while, Seb and I. I’m staring up at the circles of blue crystals.

Eventually, I hear, ‘Psst. Malk. You awake?’

‘Mmm?’

‘Are you scared?’

‘Scared of what?’

‘You know. The Dreamylater.’

‘Dreaminator. No. Why? You?’

Pause. ‘No.’

He means yes.

‘Psst. Malk.’

Sigh. ‘What now?’

‘Good luck.’

I remember the sheet of instructions:

Remember – perfect results may not be achieved straight away.