The Hardy boys began moving through the undergrowth on the trail of the four men. They crouched down and kept to the shelter of the bushes so that they were able to proceed at a good rate of speed without exposing themselves to view.
"If we can only get into the cave and get Chet and Biff free!" exclaimed Joe.
"It won't be any too easy. They seem to be guarding them pretty closely. First of all, we've got to be certain that it's them."
"I don't think there's any doubt of that. Everything hangs together too well. If we could get them out we could run for the boat and get them away to the mainland."
"That's what we'll have to plan on. But the main thing is to find this cave."
"Yes, of course."
The four men in the lead had entered the outskirts of a small grove toward the center of the island. Frank could just see the head and shoulders of the last man disappearing into the woods. He marked the spot where the fellow had entered the grove and the Hardy boys made toward it. They found it comparatively easy to follow the trail, for the others had beaten down the grass and twigs in passing, and in a few minutes they had reached the grove.
"Go slow," cautioned Frank, as they entered the shadow of the trees. "They may have seen us crossing the clearing."
They listened for a moment. They could hear the crashing of branches and the crackling of twigs, the distant hum of voices, as the quartette continued through the woods, so they went ahead.
The wood was steaming hot and the ground was dank underfoot. The grass was long and the leaves of the trees drooped of their own weight. Once Frank saw a blacksnake scurrying away through the grass, but none of the serpents molested them. The path the boys followed was beaten down by the feet of the men ahead and they made easy progress until at length the sight of a clearing ahead warned them to again exercise caution.