When they stood upon the shelf on the other side, and Ralph, having rubbed himself down with the captain's jacket, put on his clothes, Captain Horn rather sternly inquired of him how he came to do such a foolish and wicked thing as to run the risk of drowning himself in the lake at a time when his sister and his friends had already trouble enough on their minds.

Ralph was sorry, of course, that the captain had to come after him, and get himself wet, but he explained that he wanted to do something for the good of the party, and it had struck him that it would be a very sensible thing to investigate the opening on the other side of the lake. If he could get out of that great gap, he might find some way of climbing out over the top of the rocks and get to the place where his flag was, and then, if he saw Mr. Rynders coming, he could wave it. It would be a great thing if the people in the vessel which they all expected should see that flag the moment they came in sight of the coast. They might get to shore an hour or two sooner than if they had not seen it.

"If the cramp in this leg had kept off five minutes longer," he said, "I would have reached that big hole, and then, if I could have climbed over the top of the rocks, I could have come down on the other side to the front door, and asked Maka to get me my clothes, so I would not have had to swim back at all."

"That will do," said the captain. "And now that you are dressed, you can go inside and get me that woollen shirt and trousers that I use for a pillow, for I must take off these wet things."

When the boy came back with the clothes, the captain told him that he need not say anything to his sister or Mrs. Cliff about the great danger he had been in, but before he had finished his injunction Ralph interrupted him.

"Oh, I have told them that already," said he. "They wanted to know where I had been, and it did not take a minute to tell them what a splendid swimmer you are, and how you came over after me without taking as much as two seconds to think about it. And I let them know, too, that it was a mighty dangerous thing for you to do. If I had been one of those fellows who were not used to the water, and who would grab hold of any one who came to save them, we might both have gone to the bottom together."

The captain smiled grimly. "It is hard to get ahead of a boy," he said to himself.

It was late that afternoon when Captain Horn, with Ralph and the two ladies, were standing on the rocks in the inner apartment, trying to persuade themselves that they were having a cosey cup of tea together, when suddenly a scrambling sound of footsteps was heard, and Maka dashed through the two adjoining apartments and appeared before them. Instantly the captain was on his feet, his gun, which had been lying beside him, in his hand. Up sprang the others, mute, with surprise and fear on their faces. Maka, who was in a state of great excitement, and seemed unable to speak, gasped out the one word, "Gone!"

"What do you mean?" cried the captain.

Maka ran back toward the passage, and pointed inward. Instantly the captain conjectured what he meant. Mok, the second African, had been stationed to watch the lake approach, and he had deserted! Now the hot thought flashed upon the captain that the rascal had been a spy. The Rackbirds had known that there were shipwrecked people in these caves. How could they help knowing it, if they had killed Davis and the others? But, cowardly hounds as they were, they had been afraid to attack the place until they knew how many people were in it, what arms they had, and in what way the place could best be assailed. This Mok had found out everything. If the boy could swim across the lake, that black man could do it, and he had gone out through the cleft, and was probably now making his report to the gang.