In no time at all, Mr. Hampton and his party were ready to set out. Of one thing they were reminded by Jack, the individual radio sets constructed along his own lines, the instrument of which was so small and compact it was contained in the panel of a ring.

“Only trouble with these,” Jack said, “is that you can receive but can’t transmit. However—”

“However,” his father interrupted, “that is all that will be necessary.”

“Why?” asked Farnum.

“It is hardly likely that the five of us will get into such a predicament that we shall fail to return,” explained Mr. Hampton. “But the boys may be attacked when we are gone, and may be placed in a bad position. Then they can call for us.”

“At least we could send out a hurry up call over those sets,” said Jack. “As for your calling us, well, that will be a little more complicated, Dad, but it can be done, if necessary. I insist on your taking that army field set. It came in mighty handy in South America. It is no great job to set it up. And it weighs little. You are taking no other equipment, and you can afford to take it along. It won’t be in your way. Here it is, you see, all boxed up complete, handle on the box and everything.”

“Right, Jack,” said his father. “Now we can communicate with each other easily enough. Well”—looking about him—“are we ready?”

The others nodded.

“Then,” Mr. Hampton said, “I propose that we bring our canoes back through the trees, cross the island and make for the mainland on the other side.”

Farnum and MacDonald nodded agreement.

“This island is pretty long,” said MacDonald, “and it will screen our departure on the other side, in all likelihood. It is hardly likely, as a matter of fact, that we will be seen, for Lupo’s party has not shown itself since we beat off that canoe, and probably is somewhere back up that stream out of which your party came.”

“You think they cannot see the mainland on the other side of this island from there, Dad?”

“I don’t believe so,” said Mr. Hampton.

“Even if they do catch a glimpse of us,” suggested Farnum, “isn’t it probable they’ll believe we are pushing on? As a matter of fact, however, we’ll land on the mainland, and carry our canoes inland and then up along the lake till we are out of sight, when we can cross again, I suppose that’s your idea, Mr. Hampton?”

“My idea exactly,” answered the other. “Well, let’s get the canoe and MacDonald’s kayak. They have been pulled well up into the bushes, and we can bring them across the island without detection easily enough.”

“Wait a minute, Dad,” said Jack, laying a detaining hand on his arm. “If they do see you crossing the channel to the mainland, on the other side of the island, they’ll know the whole party isn’t along, and will realize you aren’t leaving, but merely carrying out some maneuver.”

“Maybe, that’s what they will think, Jack. On the other hand, they might figure some of the canoes got across beforehand. Anyway, leaving by the back door, so to speak, is our wisest plan, I am sure. The channel to the mainland on the other side is only a narrow one, and the probabilities of our escaping detection are all in our favor.”

The largest of the canoes, together with MacDonald’s kayak were dragged back through the underbrush and carried across the island to be launched on the other side. Nor did Jack neglect to load the compact field transmitting set in the canoe, as the party pushed off. Then, amid farewells from both sides, Mr. Hampton and his party set out for the mainland.

Jack watched the canoe and the kayak depart, with something of a sinking of the heart. The same feeling, he suspected, possessed his father. Neither, however, presented other than a brave and cheerful front. As for Bob and Frank, they had gotten over their disappointment at not being permitted to accompany the expedition, to a certain extent, and, cast for the first time since the start of the trip, on their own resources were beginning to enjoy the situation.

“First thing, fellows,” said Frank, as the party reached the mainland, hauled up canoe and kayak and struck into the trees, “first thing is to go to this knoll about which MacDonald spoke, and take a view of the field.”

“Yes,” said big Bob, “then let’s divide up into watches, so that the pair of us not drawn for the first watch can get some rest.”

“You certainly were born in the Land o’ Nod, Bob,” scoffed Frank.

“Yes,” said Jack, grinning, “if you’re as sleepy as all that, we’ll count you out right away. Frank and I will draw for the first watch, and you can hit the hay.”

“Not so fast,” said Bob. “I’ll take my chance with the rest of you.”

Meantime, they had been mounting the tree-covered hill to which MacDonald had referred and now, reaching the top, found that, despite its low elevation, it was still so much higher than the rest of the island and than the shores of the lake as well, that they commanded a sweeping view not only of the nearer shore to which Mr. Hampton had gone but also of the farther one whence they had come.

Not a sign of human occupation, however, was anywhere apparent. Eastward, although they knew Mr. Hampton and his companions could not have progressed far, yet the trees rimming the lake shore were sufficiently dense to hide any sign of movement. Westward, toward the farther shore, was a thick belt of trees about the mouth of the stream, thinning out farther along the shore in both directions. Neither among the trees nor on the glades, could they discern anybody although Jack, who had been thoughtful enough to bring along their field glasses, scanned the prospect through them a long time before passing them on to the others, who did likewise.

“Well, so far so good,” said Jack, with a sigh of relief. “Evidently, or so far as we can see, anyway, Dad and the rest got across undiscovered and now stand a fair chance of crossing the lake farther up undetected.”

“Maybe so,” said Frank. “Maybe, too, Lupo got discouraged and quit.”

“Retreated you mean?” asked Jack.

Frank nodded.

“Oh, you fellows are full of prunes,” said Bob. “Why should he quit now, just because we have added one more man to our forces? He’s hung to our trail a long time. That means he’s not going to quit in a hurry. No, we’ve got to keep our eyes open.”

“That’s right,” said Jack, thoughtfully, “It won’t do to get overconfident and relax our guard.”

“Just the same there’s no sign of trouble now,” said Frank. “And I’ve got a suggestion.”

“Don’t lose the idea,” said Bob, anxiously. “Hold on to it. Ideas are rare.”

“With some people yes,” said Frank, grinning. “Not with me.”

“Huh.”

Bob clutched at Frank, but the other wriggled out of his grasp.

“My idea,” he said, “is to take a plunge in the channel your father crossed, Jack. I’m hot and sticky and tired, and a swim would go fine just before I turn in and leave Bob on watch. What do you say?”

“So I’m to have the first watch, hey?” said Bob. “It’s been all decided, has it? Well, well. All right, run along, Frankie, me lad. I’m not so anxious for a swim. I’ll just start my watch here and now.”

“Bob, you’re a good sport,” said Frank, throwing an arm over the shoulders of his big chum, between whom and himself was a depth of feeling which seldom was expressed in words.

“Oh, run along and take your swim.”

Bob playfully shoved the pair of them down the hill. Laughing, they obeyed. As they disappeared among the trees, Bob selected a spot at the base of a spruce on the top of the knoll, sat down with the glasses in his lap and his eyes on the westward shore of the lake, where Lupo’s half-breeds had last been seen, and prepared to keep watch. His back was against the trunk of the tree, and he made himself as comfortable as possible.

It was a really comfortable position and, when one is tired and sitting idle, a comfortable position is conducive to drowsiness. It was so with Bob. He had had but little sleep in the last two days. He had worked hard. The air was warm and drowsy, as only the air of the short hot Summer of the north country, when the sun never sets, can be. Presently his head began to nod, and there was a buzzing in his ears as of the drowsy hum of bees. He caught himself, and sat bolt upright, rubbing his eyes vigorously with his fists. Then he leaned back against the tree trunk again, and again began to nod. This time, the jerk with which he awakened was longer in coming.

Bob got up and stretched.

“Mustn’t go to sleep,” he reflected. “Nothing in sight, though. Not much use to worry. Ho, hum.”

He resumed his seat. Imperceptibly, his eyes drifted shut. He sat through the transition period between sleeping and waking, unaware that he was yielding to slumber, merely pleasantly conscious of relaxed limbs and thoughts. Before he was aware his head nodded, his eyes closed, his chin touched his chest, and he slept.

Meanwhile Jack and Frank were thoroughly enjoying their plunge. The water was warm, there was no wind, and they swam, dived, floated to their heart’s content. Neither realized the passage of time until Frank, suddenly filled with compunction at their long absence, while Bob kept watch, scrambled ashore and looked at his watch, laid out on top of his clothes.

“Great guns, Jack,” he announced, “we’ve been gone an hour. Good old Bob. He was mighty nice about sending us off to swim while he kept watch, but you know he likes to swim, too. He’ll be thinking it’s a low trick on our part to stay so long. Maybe he’ll want to come and take a plunge himself, when one of us gets back to relieve him.”

Jack also had a guilty feeling and, as is the way with most of us, attempted to make excuses.

“He might just as well have come along,” he said. “Nothing’s going to happen.”

They were pulling on their clothes.

Suddenly they heard Bob’s voice raised in a distant shout, calling their names. Then followed a brisk outbreak of rifle shots.