‘I’m going back,’ I told him.

‘It’s two minutes further, mate.’ His voice was warm all of a sudden. We’d never been close friends, but, like all my enemies at Five Oaks, there’d been a time when we were on decent terms.

I looked back up the hill. The visibility was terrible. There was every chance I’d struggle to find the tents again on my own. Crouching, I eased myself between the two fence rails.

‘There’s a good boy,’ he said, pressing on so that I had to hurry not to lose sight of him.

It was more than two minutes further. A lot more. The cold air chilled my tracksuit against my skin. Vapour plumed from my mouth with each short, shaky breath. Dimi’s pace slowed as the trickling sound of water became louder. We were approaching the river – we’d walked along here during the orienteering.

The timber hut high on the bank had caught my attention that afternoon. Barely more than a ramshackle tree house, its presence was innocent enough. But the sight of its windowless exterior, hovering part-way over the flowing water below, had unsettled me the previous afternoon. Like passing a burnt-out house, like handling an old gas mask, its curious menace had reached out to me. And now, maybe twelve hours later, I was back.

The doorway was just two steps above the ground, the far end of the cabin high in the air, cantilevered off the bank.

‘After you,’ Dimi said, waving me inside.

It was not until I looked inside that I realized the other end of the hut also had an open doorway, from which there was a sheer drop to the river below. Just beyond the opening a thick rope dangled over the water, tied to an overhanging tree bough. It was clear that this was another of the fort’s activities – swinging across the river and landing on the wooden jetty on the opposite bank.

The floor squawked as I stepped inside.

‘Hello, Oliver,’ Nate Mackie said. ‘Good of you to stop by.’

I spun round and found his pasty face glowing like a clouded full moon in the corner next to the door. I staggered to the other side of the cabin.

‘Watch your step,’ said Joey, crouched in the opposite corner. I veered backwards to avoid stepping on him. Dimi stood with outstretched arms and legs, blocking the door I’d come in through.

I shuffled away until I was almost at the doorway at the river end, my eyes flitting between the two brothers and Dimi’s grinning face. Joey reached between his legs and drew something towards him with a familiar clacking noise. His smile widened as he slowly raised the crossbow pistol until the tip of the bolt was aimed at my chest.

‘This is more fun than shooting a fox, isn’t it, Morcombe?’ he said.