From somewhere – my conscious mind, wherever that is right now? – drifts a warning. How did it go? Inside your mind is bigger than the outside, Malky …

‘Malky!’ shouts Seb. ‘Come ooooon!’

I give in. He’s right on one thing: we can wake up and come out of the dream whenever we want. That bit I can still control, at least. And the minute the crocodile appears we’re out of here.

I have never made a bigger mistake.

‘All right,’ I say, quickly, before I can change my mind. ‘We can catch them up. They won’t have got further than the lake. And promise me: when I say we quit, we quit, okay?’

‘Promise,’ says Seb. But I’m not sure he’s really listening.

Chapter 2

We set off at a trot, each of us clutching a spear with a tip of sharp flint, and a thick wooden club with a fist-sized rock securely tied on one end with strips of leather.

We get to the end of the beach – exactly like the real beach where we live in Tynemouth (apart from the mammoths, obviously) – and run up the hill until we’re staring out over the huge plain where, in maybe ten thousand years’ time, there will be a wide road, and a pub playing live music, and a housing estate of low-rise flats. Now there isn’t any of that. There isn’t anything made by humans – apart from an old-fashioned airship that’s floating past in the sky above, shaped like a giant goldfish. Don’t ask me what it’s doing there. Dreams are weird like that and, by now, I’m kind of used to it.

There is no sign of our friends, though.

I say, ‘Super-sprint. Dream-style. You up for it?’

Seb grins gappily, and in an instant we are sprinting across the windy plain like a pair of Olympic runners battling for the finish line. Side by side, weapons in hand, I’m edging ahead of Seb, and then he pulls level as the Gravy Lake comes into view in the far distance. Then he’s ahead of me. He remains ahead as we descend the side of the shallow canyon where there is a green river of minty custard (this is a dream, remember?) and we hop across the exposed rocks and up the other side.

I let him get a good lead so that he will think he is winning. Then it’ll be an easy matter to lengthen my stride, judging it finely so that I can overtake him and win at the last minute, but not humiliate him so that he won’t want to race again.