In spite of Joe Hardy’s predictions that the marauder would be back for his notebook, that afternoon and the next day passed uneventfully on Cabin Island. No one had appeared in the vicinity of the rocks, for the boys examined the place carefully in search of footprints and the snow was still unbroken.

The mystery surrounding Hanleigh, John Sparewell, and the Bender postage stamp collection was gradually receding into the background. But to the Hardy boys it still remained a matter of great concern, especially to Frank. Each evening he sat down and puzzled over the strange cipher, vainly trying to solve the mystery it presented.

“Can’t you figure it out?” asked Joe.

“It beats me,” said Frank, flinging down his pencil. “Once in a while I think I’m on the right track, then something always happens and I find I’m farther away than ever.”

“Let the cipher look after itself. Something will turn up, I’m sure,” put in Chet.

“But if we could only find the message of the cipher, we wouldn’t have to wait for something to turn up.”

Chet looked at the message again. He shook his head.

“It’s too much for me. Don’t let it spoil your holiday, Frank.”

“You know what I’m like when there’s a mystery in the wind. And this is one of the most mysterious puzzles we’ve ever tackled.”

“We’ll get to the bottom of it yet. I’m sure of that. Just wait. Something will turn up,” said Joe.

The next day, the boys were outdoors from morning until night, skimming over the surface of the bay in their iceboats, skating on an improvised rink down by the shore, and enjoying themselves on the ski slide. Frank, for the time being, seemed to have dismissed the mystery of the notebook from his mind. That evening, as the boys sat in front of the fireplace, the Sparewell case was not even mentioned. It was a windy, stormy night and the cabin creaked in the gale.

“Must be a good, strong chimney to hold up in a wind like that,” remarked Chet.

“Why shouldn’t it?” said Biff. “It’s made of solid stone.”

“I know; but the wind gets a terrific sweep when it hits this island. That chimney isn’t so new, either.”

“Stone chimneys will last a hundred years,” scoffed Joe.

Chet pointed to the big fireplace.

“This one won’t. Look. You can see where it is cracked already.”

The boys inspected the chimney. They saw that Chet had noticed something that none of them had observed before. There was a distinct crack across the surface of the stone near the ceiling.

“It doesn’t look any too secure at that,” remarked Frank. “A crack like that might easily cause a fire.”

“It sure could!” exclaimed Biff.

“I don’t worry about fire so much as the danger that the chimney might come tumbling down in a high wind,” Chet said. “If there is one crack like that, there may be others, higher up. And if the chimney ever gave way⁠—wow!”

“We would certainly have a nice little shower of stone,” Biff said. “Well, why go looking for trouble? Wait until it happens.”

Chet insisted that he was not looking for trouble, but that he was merely pointing out what might happen. Just then there was a particularly violent gust of wind. The cabin shook. The chimney was staunch.

“I think it’s good for a few years yet,” Joe said. “Why worry?”

Their conversation about the chimney, however, was to be recalled to the boys very forcibly later on.

The next day it was Joe’s turn to remain at the cabin as “chief cook and bottle-washer.” The others went out in one of the iceboats and made a trip as far as the village. They did not stop at the little place, being in no mind to incur any of Amos Grice’s long-winded conversation, and turned about, sending the fleet little boat swooping down into the wind. They were about a quarter of a mile from the cabin and just debating the advisability of making a trip down into the cove when they heard a sound that aroused them to a high pitch of excitement.

Crack!

Sharp and clear, the sound carried through the winter air.

“The rifle!” exclaimed Frank.

“Somebody down at the rocks!”

Frank swung the boat around toward the island. The wind, however, was against them and he could make little speed. He was obliged to tack about for some time, while the others speculated impatiently on the reason for Joe’s signal.

“Just when we need speed, the wind is against us!” groaned Biff.

“Perhaps the fellow will clear out before we can get back.”

“Not if I know it,” said Frank grimly. “We’ll come around on the other side of the island, and if he is making a getaway we can head him off.”

The boat seemed to labor slowly forward at a snail’s pace. Anxiously, the boys peered toward the island.

They could see no one.

“Perhaps the shot didn’t scare him away,” said Chet hopefully.

They circled around until at last they had a full view of the side of the island on which the stolen supplies had been hidden. The ice was bare. The hillside was bleak. There was no sign of any human being.

The boys brought their craft around until they were close to the rocks. They could see footprints in the snow.

“There was somebody here, all right,” said Frank, in excitement.

“I wonder if it was Hanleigh!”

“We’ll mighty soon find out.”

They brought the boat inshore and took in the sails. Then they scrambled out, made their way up over the rocks, and examined the footprints. They did not lead up toward the cabin, but instead they led along the shore around the bend.

“Follow him!” said Chet.

“Not yet,” Frank advised. “I think we’d better go up to the cabin first and find out what Joe knows about it. Perhaps he recognized the fellow and saw where he went.”

They ploughed through the snow up to the top of the slope. They found Joe awaiting them in the door of the cabin.

“Did you see him?” shouted Frank.

“Just caught a glimpse of him,” returned Joe, as the boys came running up to him. “I happened to look out the window and caught sight of somebody down among the rocks.”

“Who was he?”

“I don’t know. His back was turned to me, and he was crouching over. He was looking for that notebook, all right. I waited for a while, but I still couldn’t get a good look at him, so I went and got the rifle. By the time I got back to the window he was gone.”

“Before you fired the signal shot?”

“Yes. I could hardly believe my eyes. He just seemed to disappear into thin air. Well, I didn’t lose any time firing the shot, I can tell you. I could see your boat away up the bay.”

“The wind was against us,” said Frank. “We tried to get here quickly, but we didn’t have any luck.”

“He’s still on the island,” said Joe quickly. “I’m pretty sure of that.”

“Wonder how he got here,” remarked Chet. “There isn’t any other iceboat around, that we saw.”

“Probably walked over from the mainland,” Frank remarked. “Well, I guess we had better explore a bit and see if we can’t get a sight of him. You’re sure you didn’t recognize him, Joe?”

“No. I couldn’t say if the man was Hanleigh or not. I didn’t get a good look at him at all.”

“We’ll get a good look at him,” growled Biff. “And mighty soon, too.”

“I suggest that two of us take the north side of the island and the other two take the south,” said Joe.

Frank shook his head.

“Someone must stay here,” he decided. “We don’t want to run the risk of losing our supplies again. If this fellow managed to draw us far enough away from the cabin, there’s no telling what damage he might do. Joe, I think you had better stay here. If you see the man coming this way, fire another shot, and we’ll come a-running.”

“Good idea!” approved Chet. “I think we all ought to separate. Each go in a different direction. If we catch sight of him, whistle!”

Frank quickly directed the search. Joe was to stay at the cabin, Chet was to go to the northern side of the island, Biff was to explore the south. Frank himself was to cut through the trees in the center of the island, emerging on the other side.

They separated.

Frank ploughed through the snow, heading toward the heavy growth of trees at the top of Cabin Island. He soon reached a point from where he could get a good view of the entire island. He could see Biff and Chet industriously exploring the shore lines.

A little distance away, in the snow beneath the trees, he caught sight of a line of fresh footprints.

He picked up the trail at once, and followed the marks in the snow.

They led him in and out among the trees, then veered and seemed to be directed toward the rocks.

“What am I thinking of?” said Frank, to himself. “I’m not following the man’s trail at all. I’m going back on it.”

He turned, and retraced his steps, after a while reaching the place where he had first found the footprints. He went on from there, deeper into the thicket, proceeding cautiously.

At last he stood still for a moment, listening. Then he slipped in behind a tree.

He heard a crackle of branches. Someone was moving about among the trees, only a few yards ahead.

Frank peeped out.

He saw a dark figure emerge from behind a clump of evergreens. The man stepped out, looked cautiously about, then moved up the slope in the direction of the cabin.

“Hanleigh!” said Frank, under his breath.

Frank Hardy’s first impulse was to whistle, in order to bring the others to his assistance. Then he paused.

What did Hanleigh want? What did he plan to do?