‘What? What are you saying? Let go!’ I grab my T-shirt and pull back. He yanks hard and my pocket rips off in his big hand. I stagger backwards again.

‘What d’you do that for?’ I say, shocked and furious.

The boy looks at the torn-off pocket in his hand, then back to me. Suddenly he roars, his eyes narrow with vicious fury. He leaps at me again.

Screaming, I turn and run back along the beach towards the reeds. But when I don’t hear him at my heels, I glance back.

The boy is lying in a crumpled heap on the sand like a dropped puppet. Has he collapsed? Or is he just pretending? Trying to trap me into going back to check on him … and then … BAM … he’ll pounce on me again? Playing dead.

My heart’s thudding like an engine. I look around again for Beaky and Lamont. Where are they when I need them? I squeeze myself into the reeds and crouch down so that I’m hidden. I watch the boy. Why did he attack me? What’s the matter with him?

I’m hiding right next to the river pool where I found him; I look at the rock where the boy bashed his head – its jagged tip is still red with his blood; it looks like a miniature model of an erupting volcano. How did he end up in the river anyway? And did he just … slip over or … ? My imagination whirs with possibilities, all of them awful. And then I notice something: there, jammed between the jagged rock and its neighbour, is a long pale stick, unusual-looking, sharp at one end. A breeze rustles the reeds.

‘A spear?’ I whisper.

Cautiously, keeping my eye on the boy, I wade into the shallow water, free the spear and pick it up. It’s beautiful, as tall as me and made from wood whittled white, with all the bark stripped off. At its tip the pointed spearhead is held fast to the shaft with twists of twine. I look closer and I see that it’s a flint, carved to a point, just like the microlith I have in my collection at home. Tentatively, I reach up and press my finger to the tip of the spearhead; it’s as sharp as a claw. This isn’t a toy. This is a real spear.

I hold the spear in the middle, where I imagine the boy holds it because the shaft here is more smoothed and worn. My hand fits his handhold perfectly. I move the spear back and forth above my shoulder, like it’s a javelin.

‘Speeeaaa!’ I say quietly, trying out the shape of the boy’s odd voice.

I look back towards the boy’s crumpled body. Why is he running around in Mandel Forest dressed in animal skins and carrying a spear? He still hasn’t moved.

Little bubbles of worry rise up from my belly. I’m worried the boy might attack me, but I’m even more worried he might actually be dying. That can happen with drowning – Mum told me – you can nearly drown and then you seem perfectly OK for ages but a bit of water got trapped in your lungs without you even knowing and it drowns you later when you’re back on dry land. Horrible!