“If they knew, they’d be out here making faces at us,” retorted Darrin wisely.

“And ordering us to get off the earth,” supplemented Greg, in a whisper.

“Listen,” whispered Dick.  “Perhaps we can guess what they’re doing.”

“I can guess what they’re doing,” murmured Reade, who had now moved around to the front with his chums.  “I’ve been watching the smoke of that fire come up through the chimney.  Humph!  I don’t believe Rip and Dodge are doing anything worse than a little camping.  There must be a stove in there, and they’re cooking some supper—–­playing at camping out.”

“I don’t smell anything cooking in there,” rejoined Dick with a shake of his head.  “We can’t hear anything sizzling over the fire, either.”

“Then what-----” began Harry curiously.

Bang! interrupted a crashing explosion inside the building.  Boom!  Then the door flew wide open, followed by a single great belching of white smoke.

Through the center of this cloud was hurled a human figure.  A man struck the ground and lay there, senseless or lifeless, a pool of blood quickly forming on the ground beside him.

Chapter II

THE VANISHING MAN

For the first few seconds the Grammar School boys stood as if chained to the ground, their eyes staring with alarm and horror.

They stared at the man, apparently of middle age, who lay there, and they beheld the blood.

What on earth could have happened?

Boom!  It was a lesser explosion that now sounded inside, yet it was enough to galvanize the boys into action.

“Come on!” cried Tom Reade, setting off in the lead.  “We don’t know nor care what’s in there!”

“The house may blow up next,” added Greg, following him.

All the members of Dick & Co. were now in full retreat.  They were courageous lads, but, with the immediate landscape in seeming danger of blowing up, getting away was the wisest possible course.

“Say, what do you make of that?” demanded Greg breathlessly, when the Grammar School boys had halted, well out of sight of the cottage and down in the woods.

“Bang!” replied Tom dryly.  “That’s all I heard.”

“And blood,” almost chattered Hazelton.

“But what it means is a big puzzle,” Dick added.  “If Rip and his crowd are or were in the cottage, they would hardly explode anything purposely and perhaps kill a man.  That man appeared to be dead—–­he must be dead.  Rip and Dodge are mean fellows, but they’re hardly up to killing people.”

“There was an explosion,” remarked Tom judicially, though his voice was still husky.  “Now, while I don’t know everything, I believe there always has to be an explosive in order to bring about an explosion.  Am I right?”

“You stand on ground that no one can dispute,” nodded Dick.  “But how did the explosive come to be in a building that belongs to the water company, and which is supposed not to have been occupied in some years?”