“What does it do?” asked Dillon, who had taken a great interest in the thing.

“It throws a bomb which emits suffocating gases without risking the lives of the police,” answered Garrick.  “In spite of the fragility of the bombs that I have here, it has been found that they will penetrate a wooden door or even a thin brick partition before the fuse explodes them.  One bomb will render a room three hundred feet off uninhabitable in thirty seconds.  Now—­watch!”

He had exploded the gun by hand, striking the flat head of a hammer against the fulminating cap.  The gun gave a bark.  A low, whistling noise and a crash followed.

“Too short,” muttered Garrick, elevating the angle of the gun a trifle.

Quite evidently someone was moving in the house.  There was a shadow, as of someone passing between the light in the upper story and the window on our side of the house.

Again the gun barked, and another bomb went hurtling through the air.  This time it hit the house squarely.  Another followed in rapid succession, and the crash of glass told that it had struck a window.  Garrick was sending them now as fast as he could.  They had taken effect, too, for the light was out, whether extinguished by gases or by the hand of someone who realized that it afforded an excellent mark to shoot at.  Still, it made no difference, now, for we had the range.

“The house must be full of the stifling gases,” panted Garrick, as he stopped to wipe the perspiration from his face, after his rapid work, clad in the heavy coat.  “No man could stand up against that.  I wonder how our friend of the garage likes it, Tom?  It is some of his own medicine—­the Chief, I mean.  He tried it on us on a small scale very successfully that night with his stupefying gun.”

“I hope one of them hit him,” ground out Dillon, who had no relish even for the recollection of that night.  “What next?  Do you have to wait until the gases clear away before we can make a break and go in there?”

Garrick had anticipated the question.  Already he was buttoning up his long coat.  We did the same, mechanically.

“No, Dillon.  You and Jim stay here,” ordered Garrick.  “You will get the signal from us what to do next.  Tom, come on.”

He had already dashed ahead into the darkness, and I followed blindly, stumbling over a ploughed field, then a fence over which we climbed quickly, and found ourselves in the enclosure where was the house.  I had no idea what we were running up against, but a dog which had been chained in the rear broke away from his fastening at sight of us, and ran at us with a lusty and savage growl.  Garrick planted a shot squarely in his head.

Without wasting time on any formalities, such as ringing the bell, we kicked and battered in the back door.  We paused a moment, not from fear but because the odor inside was terrific.  No one could have stayed in that house and retained his senses.  One by one, Garrick flung open the windows, and we were forced to stick our heads out every few minutes in order to keep our own breath.