It’s different. That’s all I can say right now, looking round the familiar cave where Seb and I have started so many of our adventures. This is the biggest adventure of them all, and he’s not here. I was hoping I’d start this dream where I left Seb – in the clearing with the big guys who captured him. That would have saved time. My subconscious had other ideas.

How is it different? Everything looks the same. There’s the fire, not even smouldering any more; there’s the drawing on the cave wall still: the car that made Seb laugh when he drew it imagining people discovering it in thousands of years’ time. Outside, the cold wind blows just like the book says, and little clouds of sand puff up and disappear in the breeze. Even the fish-shaped airship is drifting in its usual place.

I feel different: that must be it.

It’s not just that I am nervous – although I am. It’s that this is no longer fun. Mola’s words come back to me: ‘It’s like a video game to you, innit? Bam-bam-bam, now I’m dead, press “replay”, new life.’

I find myself saying aloud, ‘Well, it’s not a game now, Mola.’

‘Good, I’m glad you realise it,’ she replies. I swing round and there she is behind me and I gasp. ‘You took your time, Dream-boy,’ she says, but she doesn’t sound angry, just impatient.

‘I … I … couldn’t sleep. Hang on … this is a dream, right?’

The old lady rolls her dark little eyes like a teenager. ‘What you think? Course it is.’

‘But … but how come you … I mean …? Are you sharing my dream, or am I just dreaming you?’

‘You gonna waste time worrying about this, Dream-boy?’

‘No, but … why? Why are you here?’

‘You might need some help. Actually … Susan thought you might need help. Now tell me this: how much you wanna get your brother back?’

What sort of question is that? ‘More than anything, Mola! Even more than that!’

She narrows her eyes and nods. ‘Hmm. Sounds like a lot. Come on then. We got a run ahead of us.’

She’s off. We have to get up the beach, up the hill and across the great plain to the canyon, then on to Gravy Lake, before we get to the clearing where Seb was captured. Beside me, Mola runs without even panting. She has lifted up her ankle-length sarong, and her pale legs, knobbly and veined like a crumbly blue cheese, match mine stride for stride.

Soon we’re sprinting across the windy plain, with the Gravy Lake in the distance.

‘Mola!’ I pant. ‘All this super-fast running. It … it will use up my dream-control-power thingy.’

‘So? You got a better idea?’ She’s still hardly even out of breath. ‘You took long time to get here. We not got time for walking.’

She runs ahead of me and soon we are approaching the canyon with the green river of mint custard. I’m beginning to tire, even though I’m dream-running but still: this is going okay, I tell myself. I stop at the river’s edge and sink to my knees, my chest heaving. I count the exposed rocks poking above the surface and forming a route over the water: five steps and I’ll be across.

One of the rocks, though, looks longer than I’m used to. Greener, knobbly. And is it … is it moving?

‘Oh no, no, no,’ I murmur to myself, and I scramble to my feet again. As I watch, the rock rises up a little more and a yellow eye blinks at me slowly as Cuthbert shoves his snout out of the river and starts gliding towards me.

‘Friend of yours?’ says Mola, but my throat is too dry to answer. I’m thinking of my options. I could dream up a Nerf gun? They were pretty effective, only …

Hang on! What about a real gun?

‘Good idea,’ says Fit Billy who has appeared beside me, unexpectedly, just like in a normal dream. Instead of dumbbells, in each hand he holds a huge gun. ‘Can I recommend this?’ He tosses me a gun, which clatters at my feet. ‘A classic Thompson sub-machine-gun. Standard US Army issue throughout World War Two. That model’s the M1A1, slightly lighter. You wanna be careful with it, son. Canny firearm, that is!’

‘Thanks, Billy.’ I crouch to pick it up. When I look again, Billy has gone, but Cuthbert is now coming out of the water. The machine-gun is about a thousand times heavier than Seb’s plastic Nerf gun and I heave it to my shoulder.

‘All right, you! I’ve got you now.’ I squint through the sights, making sure the crocodile is exactly where I want him, and squeeze the cold metal trigger gently, then harder, then harder …

The closer Cuthbert gets, the better my chances of hitting him; but, if I miss, his chances of getting me increase hugely. If he does that, I’ll wake up, and I can’t risk that in case I don’t get to sleep again.

I let the crocodile get closer and closer. Mola is a few metres away, further up the bank. ‘Careful, Dream-boy!’ she warns.

Cuthbert’s jaws open: a direct hit, right in the gob, is what I need. One last squeeze of the trigger, and

BAM BAM BAM BAM BAM BAM BAM BAM BAM BAM BAM BAM BAM BAM!

The noise is painful in my ears, but I hold my arms and shoulders steady, keeping the gun aimed directly at Cuthbert. I let off another round.

BAM BAM BAM BAM BAM BAM BAM BAM BAM BAM BAM BAM BAM BAM!

I lower the gun, expecting to see the corpse of a huge crocodile lying in the shallows by the river bank.

‘I say, old boy. Doesn’t seem to be working, does it?’ drawls Cuthbert. ‘Daresay that’s the thing with dreams, hey? Don’t always do what you want! Ah well, tally-ho!’

He runs towards me on his stumpy legs, and I drop the gun. I’ve backed up to the steep bank of the canyon, but I can’t get up it because I can’t get my hands on the handholds, and …

… The croc is getting nearer – like much nearer. The wall of the canyon stretches upwards and I try again to scramble up it without success. I turn back to Cuthbert, and I can see the glint of his teeth.

‘STOP!’ I shout. ‘Stop! Oh man – please just stop!’

Cuthbert darts his long head forward, his jaws clamping down on my foot with agonising force as he starts to pull me towards the water. ‘No! NO!’

From further up the bank, Mola is running to help, shouting, ‘Get off him! Get off him!’

I’m wriggling and twisting, but the more I try to pull my foot out of the croc’s mouth, the harder he grips me, and I kick my other leg and it can’t move properly, because it is tangled up in the duvet …

And I’m sweating in bed, my foot is burning with pain, there’s a book resting on my face, which is dislodged when I move my head, the Dreaminator glows above me and I realise with a sob of frustration and a surge of despair that I have woken up.

‘No!’ I thump my head back on my sweat-damp pillow.