Suddenly Slim whirled around, his face pale, his muscles tense, and with a motion to Jerry signaled silence. As the latter removed the gear from his head, Slim tiptoed across the room to him. Placing his lips close to Jerry's ears he said: "I thought I heard someone in the battery room. Listen!"
There was no doubt of it this time. Both boys heard the sound. It was of someone softly feeling about, as though in doubt as to his exact position.
"Quick!" hissed Slim into Jerry's ear. "You get the captain and lieutenant; I'll wait here."
And as Jerry disappeared through the room in which Joe was sleeping, so as not to give suspicion to the man in the battery room, Slim slid into Jerry's chair and centered every faculty upon listening to the almost inaudible movements in the next chamber.
He could tell instinctively that the man was feeling about the walls with his hands. And not unnaturally, recalling Joe's experience only a few hours before, it gave Slim a creepy sort of feeling.
Then all sound ceased. Try as hard as he would, he could not hear a thing. He rose from the chair and went closer to the intervening door. All was silent!
A few seconds later the captain and lieutenant, accompanied by Jerry, came hurrying into the room. Without an instant's delay the captain turned the knob and they entered the battery room, switching on the light at the same time.
Apparently not a thing had been touched, but the outer door was ajar. The lieutenant jumped to it and peered out, but no one was to be seen. He closed and locked the door and began an inspection of the batteries.
"Everything seems to be all right," he said finally; and then, his eyes traveling to the table, he stopped short.
"The wireless instrument," he gasped. "It's gone!"