He began adjusting the tuner and detector knobs and sending out his signal.
[CHAPTER XXVI—A SURPRISE ATTACK]
“I hear someone coming,” whispered Bob.
While Jack continued working at the radio, Bob and Frank listened intently. Jack began speaking into the transmitter, indicating he had opened communication with the Sub Chaser. Bob put a hand on his arm, and set his lips to Jack’s ear.
“Tell ’em to wait,” he whispered. “Someone coming. Mustn’t risk being overheard.”
Nodding, Jack breathed an injunction to wait into the transmitter. All three chums sat silent and tense. The faint sound first noticed by Bob grew louder. Footsteps were approaching along the trail. Not those of one man but of a number. Fortunately, the bank of the stream was high and they were sheltered below it. Besides, down here at the bottom of the canyon, with the narrow walls not far from the stream on either hand, it was dark as a wolf’s mouth. Even to each other they were almost undistinguishable thickenings in the gloom.
The footsteps came closer. They could hear men
passing on the trail above. Frank, who was nearest, suddenly swung ashore. Bob divined he was going to clamber up to watch the trail, and considered it a risky proceeding. He put out a hand to stop Frank, but too late.
Not even daring to whisper, Bob and Jack held their places in the boat and watched Frank’s figure melt silently into the darkness.
Presently the sound of men passing ceased. Not a word had been uttered among them that Bob and Jack could overhear. Nor had the chums ventured to speak to each other. What had become of Frank? Bob looked at his watch with the illuminated dial. Ten or twelve minutes had passed. There was no longer any sound on the trail above. He could stand the suspense just about three minutes more, he whispered to Jack, and then he, too, would take the trail to see what had become of Frank.