The culvert that had brought us from the chimney to the glow-worms came to an end halfway up one wall of the cave. In front of us there was as much space as if we had in fact been astronauts. The comfort of our torch beams was lost in it. We could not see a far side; and the roof was made up of a ribbing of stalactites. Some hung down like the jagged tooth of a dinosaur; others were delicate white fingers. On the walls and in the roofing above us the starry lights of the glow-worms winked and trembled wherever the torchlight did not touch.

We stood watching in rapture. It was the dog who broke the spell. He whined uneasily, and stretched his head over the drop at our feet. Matt too looked down, and took a quick step back.

“Don’t get too near the edge,” he cautioned. “You won’t touch the sides if you fall.”

I should have known better, but I couldn’t resist taking a look for myself. I shone my torch down, and vertigo swept over me. I managed a reeling step back, and sat down quickly to settle the crazy dance in my stomach. I don’t claim I’ve ever been good at heights. And now we were stuck on the lip of a sheer drop that had no visible bottom.

Slick had a better idea than mine. He lay on his stomach, and extended his arm into space before switching on his torch. He scrutinized the wall below us methodically, turning his head from side to side. He withdrew from the brink and sat up.

“We are vertically challenged,” he announced. “We ain’t going down that way.” He picked up a loose piece of rubble from the floor and threw it casually into space. We all waited. I started counting late, and had reached five when a faint splash reached up out of the darkness.

“From this experiment,” Slick said, “we may deduce two things. It’s a long way; and it’s wet.” He was enjoying himself. I hated him. Why wasn’t he as worried as Matt and I were?

I knew Matt was worried because of his silence. Matt never shared his concern; he just hugged it to himself and worried it in secret. Mum said he was the worst worry-wart in the whole family: now I could see why she said it. Matt’s silence was like a scream, and it made me nervous.