They had wandered for a good way in the cave by now, without finding anything of interest beyond the boxes and chests of all kinds of goods. Then they came to where a pile was very neatly arranged, with numbers chalked on boxes that were built up one on top of another. Julian halted.

“Now this looks as if these boxes were about to be shifted off somewhere,” he said. “All put in order and numbered. Surely the exit must be somewhere here?”

He took George’s torch from her and flashed it all round. Then he found what he wanted. The beam of light shone steadily on a strong, roughly-made wooden door, set in the wall of the cave. They went over to it in excitement.

“This is what we want!” said Julian. “I bet this is the exit to some very lonely part of the moors, not far from a road that lorries can come along to collect any goods carried out of here! There are some very deserted roads over these moors, running in the middle of miles of lonely moorland.”

“It’s a clever organisation,” said Dick. “Lorries stored at an innocent farm, full of goods for hiding in the tunnel-caves at a convenient time. The train comes out in the dark to collect the goods, and takes them back here, till the hue and cry after the goods has died down. Then out they go through this door on to the moorlands, down to the lorries which come to collect them and whisk them away to the black market!”

“I told you how I saw Peters late one night, locking up the barn, didn’t I?” said Jock, excitedly. “Well, he must have got the lorry full of stolen goods then — and the next night he loaded them on to the spook-train!”

“That’s about it,” said Julian, who had been trying the door to see if he could open it. “I say, this door’s maddening. I can’t make it budge an inch. There’s no lock that I can see.”

They all shoved hard, but the door would not give at all. It was very stout and strong, though rough and unfinished. Panting and hot, the four of them at last gave it up.

“Do you know what I think?” said Dick. “I think the beastly thing has got something jammed hard against it on the outside.”

“Sure to have, when you come to think of it,” said Julian. “It will be well hidden too — heather and bracken and stuff all over it. Nobody would ever find it. I suppose the lorry-drivers come across from the road to open the door when they want to collect the goods. And shut it and jam it after them.”

“No way of escape there, then,” said George in disappointment.

“ ‘Fraid not,” said Julian. George gave a sigh.

“Tired, old thing?” asked Julian kindly. “Or hungry?”

“Both,” said George.

“Well, we’ve got some food somewhere, haven’t we?” said Julian. “I remember one of the men slinging my bag in after me. We’ve not had what we brought for tea yet. What about having a meal now? We can’t seem to escape at the moment.”