Frank had learned the art of trailing from Indian guides in the West, and, for a white person, he was an expert. As a shadower, he had the skill of one who had been all his life in the business.

He did not let the man in gray get far away before approaching near enough so Mr. Cooler could be seen occasionally as he slipped through the bushes.

But it was not difficult to follow the queer old man, for Cooler did not seem to imagine for a moment that he was shadowed. He walked swiftly, puffing away at his pipe, and the smell of burning tobacco came back to the nostrils of the pursuing lad.

After a little time the man struck the path that runs round the island and through the old granite quarry. Then he walked still more swiftly, but Frank also found less trouble in following.

Soon the quarry was reached. Cooler passed straight through this and struck the track which led down the incline to the sheds near the wharf.

Now Frank was not able to pursue him so closely; he was forced to linger far behind, for to keep close meant certain discovery should the man look back.

Still he followed. The track ran through a cut and wound slowly along a bank, to one side of which lay the water.

Frank reached the cut and saw the man in gray disappear beyond some bowlders. A moment later Merry was at the bowlders, peering down the track toward the still retreating form of the little man, over whose shoulders at regular intervals curled blue puffs of smoke.

Frank had expected that the man would be suspicious and would look round frequently. He was astonished when the man did not look round at all.

"He doesn't act like a criminal," Frank decided. "He hasn't the air of a criminal. He walks along as if he had not a care in all the wide world and did not fear to have all his actions watched. It is strange—very strange."

Already Merry had learned that men who commit crimes betray themselves by certain peculiar movements. The thief unconsciously assumes the pose of a man picking a pocket, or taking what does not belong to him. The burglar crouches in his walk and steals along catlike. The guilty man often casts sly backward glances over his shoulder. It is rare for him to have the air and manner of innocence.

But this little man in gray, when, without doubt, he believed himself to be alone, was still the same care-free, careless old fellow.

He disappeared into one of the sheds at the end of the railroad. Frank had slipped yet a little nearer and watched from a place of hiding.

Five minutes passed, and then the man in gray and another man came out of that shed and took the path that led toward the old boarding house.

Frank uttered a low exclamation.

"Is it possible?" he muttered. "I believe I know that fellow with him."

He watched the companion of the man in gray. As they passed from view, he again muttered:

"I do know him! He is Dan Hicks, the cock-eyed man! That settles it! Mr. Caleb Cooler is just what I thought—he is one of the gang, and he came here to spy upon us!"

Frank ran lightly down the track, hidden by the bank beyond which the men had disappeared. He stooped as he ran. Ahead of him he saw the point where Browning had pried up the rails and sent a flat car, loaded with granite, into the water, thus saving Frank's life. He shuddered as he thought of his sensations during those terrible moments of peril while he was bound to the track and could hear the car rumbling toward him.

The bank grew lower till at last he could not keep hidden behind it if he ran farther down the track. Then he flung himself flat on the bank and crawled up till he could peer over.

The two men were walking toward the distant boarding house. Hicks was talking excitedly, while Cooler still smoked. Hicks looked back suspiciously, but the man in gray did not turn his head.

They passed the house where the overseer had lived when he was on the island with the crew of men who worked in the quarry—they were again hidden from view.

Over the bank scrambled Frank. Keeping the house between him and the men, he ran swiftly forward.

In a short time he reached the house. He paused to listen, his heart thumping loudly.

He could hear nothing.

Then he slipped round the house. He carefully peered round each corner before advancing. At the second corner he halted, for again he could see the men he was shadowing.

They were near the old building in which Frank had been struck down. The man in gray seemed to be asking questions. He was surveying the surroundings as if he had never inspected them before.

For fifteen minutes they stood there talking, and then they went into the building.

Frank decided to return to his friends. He quickly darted up an incline toward some cedars, which he saw grew thicker and thicker higher up the slope. Soon he was hidden by the bushes.

Then Frank went forward more slowly, taking pains to keep in the bushes. Up above was a ledgy height. He came to it after a time. He found a position where he could look down into the old quarry. From that position he could see the overturned car and the granite which lay in the water at the foot of the bank down which it had jumped. He could also look far out over the island-dotted bay. He could see small boats in the distance, he could see white sails, he could see the sunshine reflected on the blue water. In the midst of this mass of water and islands lay Devil Island, shrouded by mystery, lonely and desolate, shunned by man.

Once before he had strongly felt the air of desolation that seemed to hang about the place, and now the same uncanny sensation was creeping over him again. Somehow it seemed that he was far from men, far from life, lost in a lonely waste of water, cast on an uncanny island.

He shook himself, trying to throw off the feeling. He wondered why it should come upon him at that time, and then he began to remember how he had first felt it once before when near that very spot.

"The glade—the grave in the woods!"

He muttered the words, realizing that the woods were close at hand. They lay there dark and gloomy. He must pass through them in order to reach the White Wings, or he must retrace his steps and take the path. To do the latter would be sure to expose him to the men he had watched.

But Frank did not wish to turn back. There was something fascinating as well as repellent about the woods. Down there was a grave. At the head of the grave was a stone. On that stone was chiseled:

"Sacred to the Memory of Rawson Denning."

Denning, like Frank Merriwell, had been inquisitive. He had attempted to solve the mystery of the island, and he had disappeared. Afterward the grave had been found on the island. No one had dared open that grave to see if the body of the missing man from Boston lay within.

Frank felt a desire to look at that grave again. He went down toward it, entering the thick woods. Every step that he advanced seemed to cause the feeling to grow stronger upon him. The woods were silent and deserted. It did not seem possible that there could be a thing of life other than Frank anywhere within them.

All at once, with astonishing suddenness, he came out into the opening and there before him was the grave, the headstone gleaming gray in the dim light.

Frank paused. Involuntarily he listened. He had not forgotten how, on his other visit to the spot, both he and Browning had seemed to hear a mysterious whisper in the air, had seemed to hear a rustle down in that grave, as if the murdered man turned restlessly. Without knowing why he did so, Frank listened again.

"Look!"

He started, for it seemed that he had heard that whisper. He glanced all around.

Silence in the woods. Not even the rustle of a leaf. How lonely it was!

"Look!"

Again that word, coming from he knew not where.

At what should he look? What did it mean?

Then he told himself that it was all his imagination—he had heard no whispered word. He advanced toward the grave; he stood beside it.

"Look!"

Was it imagination? This time the whisper sounded amazingly clear and distinct.

"Look at what?"

In spite of himself, he spoke the words aloud. He did not expect an answer, and he gasped for breath when it came:

"The stone!"

A quiver ran over Frank Merriwell's body. Of all the mysteries on this island, the mystery of this black whispering glade in the woods was the greatest.

He bent forward and looked at the stone. There were fresh chips on the mound, and at a glance he saw that the name "Rawson Denning" had been chiseled out. Below it another name had been cut into the stone, so that the inscription now read:

"Sacred to the Memory of Frank Merriwell."