While the boys sat on the deck watching the mysterious lights with puzzled eyes, there came a quick, sharp explosion and the lights disappeared. The explosion sounded like the touching off of dynamite.
Both boys arose to their feet and leaned over the gunwale of the boat, gazing down the lagoon with mystified faces.
“Alex went to bed too early!” Case suggested.
“Yes, he should have seen that little old Fourth of July celebration,” Jule replied. “Let’s wake him up and tell him about it.”
“You wake him up,” Case answered.
Jule made his way into the cabin and felt around on the bunk occupied by the boy. Teddy, the bear cub, lay there sound asleep but Alex had disappeared! Jule returned to the deck with a grin.
“That little idiot,” he said, “has left the boat again.”
“We might have known he would!” answered Case. “He runs away from the boat in the night every time he gets a chance, especially if Clay is ashore. They’ll both be back here before long.”
“Clay probably will,” Jule observed, “but we don’t know when Alex will return. We usually have to get him out of some scrape.”
In the meantime Clay was pushing steadily through the thicket which lined the north arm of the peculiar-shaped island. For some moments he guided his steps by the blue lights which seemed to him to rest upon the water. Then came the explosion which the boys had heard and the lights were no longer in view.