And then, just as Jack was almost untangled, there came a grinding, grating roar once more — and the enormous rock slid along in front of the great door and swung round slowly into its place.

Behind it, caught between the rock and the door, was everyone except Mafumu and Jack! The girls, Mike, Paul, Ranni and Pilescu were in the narrow passage between.

Ranni tried to stop the rock from sliding back into place, but once started on its way nothing would stop the enormously heavy rock. No one could escape, either, for there was no time to slip out of the trap.

Jack and Mafumu stared towards the rock in the greatest dismay. Jack leapt down from the tree, almost breaking his ankle, and ran towards the mountain.

“Are you safe, are you safe!” he shouted.

But there was no answer. The swinging rock shut the sound of voices away. Jack beat on the rock, he tried to heave it as he had seen Ranni do, and Mafumu did the same. But neither boy could find the secret balance of the rock, and it stayed where it was, colossal in the moonlight, towering above them as they shouted and hammered on it.

And then, behind the rock, the great door slid back! Jack and Mafumu heard it, and fell silent, listening. What was happening?

What indeed? When the door slid back, the little company in front of it stared with wide eyes into a great hall-like cave. It was lighted by glowing lamps, and a wide flight of steps led downwards for a little way. Up these steps came the Folk of the Secret Mountain, dressed in their flowing robes, and carrying strange yellow wands which glittered from top to bottom.

The leader was a very tall man with a bright red beard and gleaming eyes. He spoke to Ranni in language rather like that used by Mafumu. Ranni understood some of it.

“He wants us to follow him,” Ranni said to Pilescu. “Got your gun, Pilescu?”

“Yes,” said the big Baronian. “But it’s no use using it, Ranni. There are too many of them. Put your gun away for the moment, and we’ll see what happens. We are in a nice mess now. Only Jack and Mafumu are safe!”

That was a strange journey into the heart of the mountain. Big carved lamps glowed all the way, lighting up enormous flights of steps, great walls, and high rocky ceilings.

“The mountain is full of hollows which these people have made into halls and rooms,” said Ranni in a low voice to Pilescu. “Isn’t it amazing? Look at those great pictures drawn in colour on the walls! They are strange but very beautiful.”

The children gazed in wonder at the great coloured pictures on the rocky walls of the mountain-caves. Lamps were set cleverly to light up the pictures so that the men and animals in them seemed almost alive. The Secret Mountain was indeed a marvellous place!

At last the long journey through the heart of the mountain came to an end. The little party found themselves in a queer room, whose rocky ceiling rose too high for them to make out by the light of their lamp. Shining stones were set into the walls, and these glittered like stars in the lamplight.

A rough platform was at one end of the room. On it were piled heaps of wonderful rugs, beautifully woven, and marvellously patterned in all the brightest colours imaginable. The children sat down on them, tired out.

Pitchers of ice-cold water stood on a stone table. Everyone drank deep. Flat cakes lay on a shallow dish beside the pitchers. Mike tasted one. It was sweet and dry, quite pleasant to eat. Everyone made a meal, wondering what was going to happen.

The door to their strange room was made of strong wood and had been fastened on the outside. There was nothing to do but wait. The Mountain Folk had left them quite alone in the heart of their queer home.

“We’d better get some rest,” said Ranni, and he covered up the three children with the rugs. “I don’t know what to wish about Jack. I’m glad he’s not caught — and yet I wish we were all here together.”

“Perhaps Jack and Mafumu will find some way of rescuing us,” said Peggy hopefully.

Ranni laughed shortly. “It’s no good hoping that, Peggy! If he tries to get through the rock entrance, and through that big studded door, he will just find himself a prisoner!”

“Do you suppose we’ll see Mummy and Daddy?” asked Nora suddenly. “They must be somewhere in this mountain too.”

“Yes — that’s quite likely,” said Pilescu thoughtfully. “Ranni, I’ll keep guard for the first half of the night. You go to sleep with the others now.”

In spite of all the tremendous excitement of the day the three children were soon asleep on the soft rugs. Ranni did not sleep at first, but at last he dozed off, sitting half upright in case Pilescu needed him quickly.

But the night passed away silently and no one came to disturb them in their cell-like room. The lamp burned steadily, giving a soft light to the curious, high-roofed room. It burned until the day — and even then it still lit the room, for no daylight, no sunlight ever entered the heart of the Secret Mountain.

Jack was almost beside himself with alarm and despair. Mafumu kept close beside him, saying nothing at all, looking at Jack out of his big dark eyes. Both boys beat again and again on the great rock that hid the entrance to the Secret Mountain. They heard the door behind slide back into place once more — and then all was silent.

“Come,” said Mafumu at last, and he took Jack’s arm. He led him to where everyone had left their packs, and the two sat down together.

“What are we to do?” said Jack at last, burying his head in his hands. “I can’t bear to think of everyone captured, and we can’t get at them.”

Mafumu did not understand. He sat there looking at Jack, muttering something in his own language. Then he made a kind of bed of the packs, and pushed Jack down on them.

“We sleep now. I find way soon,” said the younger boy flashing his white teeth in the moonlight. They must wait until the morning.

Jack fell asleep at last. As soon as Mafumu saw that his eyes were closed, and heard his regular breathing he crept away from Jack. He stood upright in the brilliant moonlight and looked at the great mountain. How was he going to find a way inside?

Mafumu was not yet ten years old, but he was the sharpest boy in his tribe. He was mischievous, disobedient and wilful, but he had brains. He had lain thinking and thinking of how he might get into the Secret Mountain without going through the entrance of the sliding rock.

And into his mind had come a picture of the great waterfall. He saw it springing from the mountain-side, a great gushing fall of silvery water. He was going to see if it came from the heart of the Secret Mountain!

The boy slipped away in the moonlight. He ran until he came to the great waterfall. It was magnificent in the light of the moon, and the spray shone like purest silver. The noise was twice as loud at night, and he was half-afraid.

He glanced fearfully all round him. He was not afraid of animals or snakes — but he was afraid of being caught by the Folk of the Mountain. If he should be captured, Jack would be left helpless, for he did not know the countryside as Mafumu did.

Mafumu made his way up the mountain, keeping as close to the waterfall as he could. Several times he was drenched, but he liked that. It was cool! The night was hot, and Mafumu was bathed in perspiration as he climbed upwards. The mountain was very steep indeed. It was only by working his way from rocky ledge to ledge that he could get up at all.

At last he came to where the waterfall began. Mafumu worked his way above the fall, and found that, as he had thought, the water gushed straight out of the mountain itself. There must be an underground river running through the mountain. The great hill towered above him, reaching to the clouds. Just below him the waterfall sprang from the mountain, and the fine spray clung to his skin.