A few seconds later we reached it, and all the hope and excitement drained out of me. It was more like a river than a stream. Three or four metres across.

“I can’t jump that,” Kenny said. “No way.”

I peered at the stream, trying to work out if we could wade across. There were small waterfalls – just a few centimetres high, where the water was white. And brown parts, the colour of tea, where the stream moved slowly.

The trouble was that the slow parts looked quite deep. On a hot day it would have been fun to wade and splash across. But we were already cold to the bone. To be soaked through as well as cold … I crouched and put my fingertips in the water. I thought my hands couldn’t get any colder, but this was a different type of cold. It was a killing cold.

“It’s no use, Kenny,” I said. “We’ll have to go around it.”

I got the map out of my pocket again. It was so creased now that it was hard to read. And more melted snow had got onto it, smearing more of the ink. But I could still just make out the line of the stream. I guessed roughly where we must be, and followed the stream on the map. It went back until it joined the path we’d been on. And it looked like the path went over the stream, so there must be a bridge. I let my finger follow the stream further. Just near the edge of the printed page there was a main road and another, bigger, bridge. Yet here on this hillside, lost in the snow, it felt like we were completely cut off from the rest of the world. It was a bit weird to know there was a proper road out there, cutting into this wilderness.

If we followed the stream back to the path, we’d have wasted an hour of climbing up this bloody hill. But that couldn’t be helped. Jenny used to say that sometimes you mess up. It’s what you do next that counts. There’s no mess so bad that it can’t be cleared up. Something like that, anyway. Sometimes you have to go back so you can go forward.

I tried to show Kenny the way we had to go. But he was dulled by the cold, and his eyes were glazed. He just wanted out. I put my arm around him, but I had to stand on my tiptoes to do it, as he was much taller than me.

“At least it’s downhill,” I said.

“OK.”

“And let’s keep moving. It’s freezing when you stop.”