“Lead on, Mafumu,” said the boy, taking a deep breath. “I’m a good swimmer — but I don’t know if I’m as good as you are! Go on!”

So into the river went both boys, swimming below the water where it touched the roof, and coming up, almost bursting, in the place where the roof lifted a little so that they might breathe.

Then into the water they went again, shivering, for it was icy-cold, and once more swam as fast as they could up the low tunnel, their heads bumping the roof till they came thankfully to where the tunnel opened out into the large cave! They crawled out of the water, panting, and sat down to get their breath. Their hearts beat like great pumps, and it was some time before both boys could go on.

“Now which way?” wondered Jack, looking all round at the gleaming cave. “There are three or four archways leading out of this cave, Mafumu, with the river winding silently through the middle. Which way do we go?”

Mafumu was running all round, peering first through one rocky archway and then through another. He stopped at last and beckoned to Jack. Jack went over to him, wondering what the other boy could see, for he was plainly excited.

No wonder Mafumu was excited! Peering through the little archway he had seen an enormous flight of steps leading upwards through the mountain! The steps were cut out of the solid rock, and were polished and shining. At the foot hung a great lamp, very finely made, which gave a curious green light.

The boys stood at the bottom of the rocky stairway, staring upwards. Where could it lead to?

“Shall we go up?” whispered Jack, his whisper starting a rustling echo all around him. Mafumu nodded. In silence the two boys began to climb the great stairway. It went up for a great way, wide and easy to climb. Then it curved sharply to the right and became a curious spiral staircase, still cut into the rock.

“I believe it leads up to the top of the mountain!” said Jack, quite out of breath. “Let’s sit down and have a rest. My legs are really tired with all this climbing.”

They did not notice that a wooden door opened on to the stairway just behind them. They sat there in silence, resting themselves. And then suddenly they heard the harsh voices of the Folk of the Mountain! The boys looked round quickly and by the light of one of the green lamps hanging at a curve of the stairway they saw the door. It was just opening!

The boys did not know whether the folk would go up the stairway or down, and they hadn’t time to choose! They simply tumbled themselves down the steps, came to a curve and waited there, their hearts thumping, and their legs trembling.

“If they come down the stairway we shall be seen!” thought Jack desperately. “They will touch us as they pass, because the stairway is so narrow.”

But the Folk of the Mountain went up the stairway, not down! The boys heard their footsteps and their voices disappearing into the distance. They crept back up the stairway to the door — and it was open!

“Golly! What a bit of luck!” Jack whispered to Mafumu, who, although he did not understand the words, knew what Jack meant all right. The boys slipped in through the open door and found themselves in an enormous gallery that ran round the most colossal hall they had ever seen.

“This must be a kind of meeting-hall,” thought Jack, gazing down from the rocky gallery to the great floor below. “I bet it’s right in the very middle of the mountain! Golly! What a strange place it is!”

Steps led up from the great hall in many directions. They led to fine wooden doors, studded and starred with gleaming metals. The Folk of the Mountain had a strange and mighty home! There was no one at all to be seen and the deep silence seemed very queer. Enormous lamps hung down from the roof, swinging slightly as they burned. Deep shadows moved over the floor as the lamps swung, and Mafumu stared, for he had never seen such a place in all his life.

“Mafumu! Those people will be coming back soon, I expect,” said Jack in his ear. “Come on. We must get down into this hall and go up a stairway to see if we can find where the others are. Hurry!”

The boys slipped down into the great hall. They stood there in the shadows, wondering which flight of steps to take. They chose the nearest one, a wide, shallow stretch that led to an open doorway.

Up they went, and through the doorway. A long, dark passage lay before them, with rocky walls and ceiling. They went down it, and turned into another one. They heard the noise of voices and stopped.

No one had heard them, so they crept on again, and came out through a big archway that led into a fine cave. Its walls were hung with the skins of animals and with curtains of shining material. The floor was covered with rich rugs. On them sat the Folk of the Secret Mountain.

How queer they looked in the light of the swinging lamps! The men all had flaming red beards and hair, and their faces looked a sickly yellow. The women were wrapped up to their noses, and showed neither hair nor chins! The boys knew they were the women because they spoke in high-pitched, shrill voices.

All of them were working at something. Some were making rugs. Others were weaving with bright-coloured strands that looked like raffia. Some were hammering at things that the boys could not see.

“We’d better go back,” whispered Jack, pushing Mafumu. “Come on. If we’re seen here we’d be taken prisoner.”

The boys crept back. Mafumu was frightened, for the Folk of the Mountain had looked so strange! The two boys went back until they came to another door. It was shut. They pushed against it and it opened.

The room inside was very odd. It held nothing at all but a rope ladder that went up and up and up into the darkness of the roof!

“There must be a narrow hole that goes up for a long way,” whispered Jack. “I wonder where the rope ladder leads to. Sh! Mafumu — there’s someone coming!”

Sure enough, voices and footsteps could be heard once more. Mafumu gave a groan of fright, caught hold of the rope ladder, and was up it in a trice, disappearing into the darkness of the high roof at once. Jack thought it was a good idea and he followed as well.

Just in time! Three men came into the little room, shut the door and began to talk in their harsh voices. Jack and Mafumu stayed still on the ladder, for they knew that if they climbed higher the ladder would shake and the men would guess someone was up there.

The men talked for ten minutes, and then went out. The two boys climbed up the ladder at once. They thought they would be safer at the top than at the bottom!

The ladder was fastened to a ledge, and opposite the ledge was another door, strong and heavy. It was bolted on the outside with great heavy bolts that looked impossible to move!

“Somebody’s bolted in there,” whispered Jack. “Do you suppose it’s Peggy and Nora and Mike and the rest of them?”

Mafumu nodded. Yes — he felt sure they had stumbled on the prison of the rest of their little party! He began to pull at the bolts.

Although they were heavy, they were well oiled and ran fairly easily when both boys pulled at them. One by one they slid the back. There was a kind of latch on the door, and Jack slid it up. The door opened.

Not a sound came from the room inside. The boys hardly dared to peep round the door. What would they see? Surely if their friends were in their they would have made some sound, said something or shouted something!

Jack pushed the door wide open and went boldly inside, far more boldly than he felt! And what a surprise he got!

The rest of their party were not there — but Captain and Mrs. Arnold were! They lay on piles of rugs in the corner of the dimly lit cave, looking pale and ill. They watched the opening of the door, thinking that someone was bringing them food.