twisted his head from side to side in agony.
"What is the matter with you?" shouted Peret. "Speak! I want to help you."
The stricken man made a violent effort to throw off the invisible horror that had him in its clutches. Then the muscles of his body relaxed, and he ceased to struggle. Drawing in a deep breath of air, he expelled it with a sharp whistling sound. Then, exhausted, he shook off Peret's hand, and sank down on the pavement in a sitting posture.
"Sacrebleu!" yelled Peret. "Speak to me, my friend, so I can avenge you! One little word is all I ask. What attacked you?"
"I—I don't know," the man gasped. "It—It was something I could not see! It was a monster—an invisible monster. It whispered in my ear, and then it began to choke me. Oh, God—."
His head fell forward; he began to sob weakly.
"An invisible monster," repeated Peret, staring at the man curiously. "What do you mean by that?"
Before the man could reply, the police patrol-wagon swung around the corner and, with a clang of the bell, drew up to the curb. Detective Sergeant Strange of the homicide squad and two subordinates leaped to the sidewalk and approached the Frenchman.
"Well?" demanded Strange, with characteristic brevity.
"Murder," returned Peret, with equal conciseness, and nodded at the two bodies on the pavement.
"How?" Strange shot out.
"I don't know," replied Peret. "As I was passing the house ten minutes ago, Max Berjet, the man on your left, hurled himself through the window, cried out that he had been attacked by ten assassins, and died immediately afterward. After summoning a physician, I started to enter the house to investigate, and heard the doctor scream. When I turned I saw Dr. Sprague and this man"—pointing to the pedestrian—"struggling in the grasp of something I could not see. Before I could reach them, the two men fell to the pavement. Dr. Sprague died almost instantly; this other man, as you see, is recovering. He has just informed me that he was attacked by an invisible monster."
Strange's bellicose features twisted into a grin.
"An invisible monster, eh? Well, it had better stay invisible if it's still sticking around." He whirled about, and to the patrolman: "I want all available men here on the jump, Bill. Call the coroner at the same time. O'Shane"—to one of the plainclothes men who accompanied him—" watch the front of that house and keep an eye on these bodies until the coroner comes. Mike, take care of the back of the house, and," he added with a grim humor, "keep your eye peeled for an 'invisible monster'."
Strange turned once more to the Frenchman.
"You're sure these two men are dead, Peret?"
"They will never be any deader," replied Peret shortly.
"All right—Who is that man?" pointing over his shoulder at the druggist.
"I am the proprietor of the drug store across the street," spoke up the druggist. "I ran over with Dr. Sprague, who happened to be in the store when this gentleman summoned assistance."
Strange nodded.
"I may have to hold you as a witness," was his curt reply. "Stick around until I can find time to question you. Now Peret, before we enter the house, spill the details. What do you know about this 'invisible monster'?"
"Little more than I have already told you," answered Peret, and
