“Gee!” exclaimed Carl, “I thought that was the crack of doom!”
“Get down to the machines, quick, you boys!” Ben cried out. “There may be some one trying to work them an injury.”
The two boys darted away, stopping only to secure electric flashlights, and were soon seen examining the aeroplanes. Ben waited a moment for some indications that the boys had met with a lurking enemy, and then started away in pursuit of the treacherous aviator.
He was not in time, however, to stop the fellow before his machine launched into the air. As his aeroplane rose, Ben saw that he swung his face for an instant toward the camp. For only a moment the light of the fire shone on the face so turned back. Ben thought he had never seen a more villainous expression on any human countenance.
The boy returned to the machines and joined his chums with an angry scowl on his face. He was angry at himself for having for a minute regarded the stranger in a friendly spirit.
“Where’s the artillery?” asked Jimmie, flashing his light about the aeroplanes. “I thought I heard cannonading.”
As briefly as possible, Ben explained what had taken place, and the three walked over to the spot where the missile had struck and exploded. There was a great hole in the ground, and tiny fragments of a tin can lay scattered about, lying at some distance from the hole.
“Nitroglycerine!” exclaimed Ben, picking up one of the fragments.
“That only goes to show,” Jimmie answered, wrinkling his freckled nose, “that this trip of ours is not at all like a Sunday School picnic. I wish we had caught him before he mounted his machine,” he went on. “I’d like to fill him so full of holes that he could go away and play that he was a Swiss cheese.”
There was very little sleep in the camp that night. The boys were away at daylight, and a couple of hours later saw the machines snugly tucked away in a hangar not far from the aviation field near Forest Park.