On the other side stood a big tree, its trunk and branches sharply outlined against the clear sky. At the base of this tree, with his back toward them, stood a man. Now, the surprising part of it all, and that which had caused the boys to proceed so cautiously, was the fact that the man wore headphones and was evidently receiving a message of some kind. Fastened to the tree was a box, which evidently contained telephonic apparatus. At first the boys thought he must be listening at an ordinary telephone, but the fact that he had no transmitter indicated that he was listening in on a radio receiving set.
The boys had hardly reached their place of concealment when the man turned sharply about, darting furtive glances here and there, evidently in search of possible intruders. The boys crouched lower behind the bushes and prayed fervently that Jimmy would not arrive before the man had gone. The fellow was of fair size, with a deeply tanned face, and wore a moustache. Fortunately, after they had been watching him a few minutes, he removed the earphones, placed them in the box, and, after locking it, started into the woods, following a dimly marked footpath.
It was well that he left when he did, for not two minutes later Jimmy came puffing along, looking anxiously for the others. He stopped in amazement when he saw his friends emerge from the bushes, and was about to raise his voice in vehement questionings when Bob leaped at him and clapped a hand over his mouth.
“Be quiet!” he hissed into his ear. “There’s some funny work going on here, and we want to find out what it is.”
Thus admonished, Jimmy was released, and in low tones the others told him of what they had seen and showed him the box fastened to the tree. While they were about it, they made a hasty search for the antenna, and found it strung close to the trunk of the tree, extending from the top almost to the roots. After this discovery they hurried after the man with the moustache, fearful lest they should lose his trail.
It was no easy matter to follow the dimly marked path, for it passed at times over stony ground and big boulders, where often it took much searching here and there before they picked up its continuation.
“We may be taking all this trouble for nothing,” said Bob, after one of these searches. “Maybe he’s just a lumberman receiving instruction by wireless from his employers. Big business firms are using radio more and more for such purposes.”
“I didn’t like the way he kept looking about him, as though he had something to conceal,” objected Joe. “It can’t do any harm to see where he goes, anyway. We may find out something important.”
“His hands weren’t those of a lumberman,” observed Herb. “Those hands never saw rough work nor, judging from the man’s face and manner, honest work. Come on, fellows.”
Accordingly the boys followed the difficult trail with untiring patience, and at last their perseverance was rewarded. The path widened out into a little clearing, and at the further side of this was a rough log cabin. The little shack had two small windows, and with infinite caution the boys approached until they could see into the nearest one.