"It doesn't matter much. To start with, we'll nose around among these rocks for a while."
The sun blazed on the bare crags as the boys picked their way over the rocks and boulders. Away in the interior they could see the waving tops of trees in the steaming marsh, but for the time being they contented themselves with exploring the rocky end of the island. It was quite barren and it appeared that no human being had ever set foot upon the place.
"You can't blame them, either," said Frank, when Joe had remarked on this fact. "It's certainly not a place where I'd care to build my happy home."
After about an hour of desultory search they came upon something that proved conclusively that human beings had indeed been there before them—and not long previously, at that. Charred embers and a crude fireplace built of rocks in a little hollow told the boys that someone had preceded them.
"We're on the track of something," declared Frank, as he examined the remains of the fire. "This blaze was built here not long ago. Some one has camped here." He circled the rock, which dipped toward a patch of undergrowth and luxuriant grass. "And here's a trail!" he exclaimed.
It was merely a faint depression in the deep grass, but it proved that more than one person had passed that way before. The trail wound along through the verdure, away from the shore, leading toward the interior of the island.
"Well, if some one else has gone this way, we can follow the path, too," Joe remarked. "Got your gun?"
"Yes." Frank patted his hip. Both boys had provided themselves with revolvers before leaving home. They were not adept with fire-arms, but the nature of their mission had prompted them to come prepared for any emergency. Fenton Hardy had a collection of weapons in his study, all trophies of his various cases, and the Hardy boys had each taken a small and efficient-looking automatic pistol for protection.
They struck out along the faint trail, the grass rustling about their feet. The green thicket loomed ominously before them and the heat became more intense.
Frank was striding along in advance, gazing at the thicket ahead, when he suddenly came aware of a disturbance in the grass almost at his feet. Some sixth sense warned him of danger. That strange tickling of the spine, man's instinctive reaction to the presence of a hidden peril, made him look down.