"Maybe they're warning us," Tom said. "P'raps someone is coming. What shall we do? I'll call them back."

Tom was the best whistler of them all and his answering signal was so real that David almost looked up, expecting to see the shy little bird. Then he felt Jon's hand gripping his arm and heard him say under his breath:

"Turn round carelessly in a sec. I think there's someone watching us through a little window in the doors... Don't let them see that you've noticed."

David felt his mouth go dry with excitement as he said normally, "Call them again, Tom." Then, as the peewit's lament wailed through the gloom he turned casually with his hands in his pockets and looked as closely as he could at the surface of the great doors. He kicked a pebble idly and moved a step or two nearer, pretending - and not finding this very difficult - to be fidgeting about because they did not know what to do. Then he thought he noticed a slight movement on the surface of the nearest door. Jon was right, then; they were being watched.

David felt that he could now make some amends for leaving the map behind. By a stroke of good fortune his electric torch was in his jacket pocket, although he had forgotten it until now. He had it out in a flash and calling suddenly, "Watch the doors," he pressed the button and swung the beam up until it picked out a little door about three inches square in the centre of the big, right hand gateway. As Jon and Tom wheeled round at David's warning the trap closed with a click, but not before David had seen a human eye watching them. It had disappeared before he could have counted three, but not before it had given him a shock.

Not only was there something unpleasantly different about the eye, but the idea of someone watching them while refusing to answer the bell was maddening. David felt himself go hot with anger and was surprised to hear his own voice shouting, "Whoever you are please open the doors. We're lost and we need help."

And Tom, who had also glimpsed the sinister eye, rushed forward and banged on the doors with his fists.

"Let us in!" he yelled. "Open the door. Answer us."

They waited for another minute and then called again, but there was no sound which even suggested life within these strange, grey walls. Then Jon said quietly, "That's very odd. I think we'd better go back to the others as we're not going to get any help here. Come on."

Half-way up the rough track which led to the wood they heard running footsteps coming towards them.

"Whistle, Tom!" David said urgently. "Quick!" Again the call wailed and this time was answered - but not with a whistle.

"It's me! Penny!" a familiar voice called, and then she was with them and clinging to Jon's arm.