JULES PERET, known to the underworld as The Terrible Frog, hated the foul air in crowded street cars and the "stuffiness" of a taxicab, and, whenever possible, he avoided both.

Hence, having nothing in view that demanded haste, after leaving police headquarters, he had, in spite of the lateness of the hour, elected to make the journey home on foot. He had not gone very far, however, before he began to wish that he had chosen some other mode of traveling, for he had scarcely ever seen such a gloomy night. It was January, and the atmosphere was of that uncertain temperature that is best described as raw. The darkness was Stygian. A fine mist was falling from the starless skies, and a thick grayish-yellow fog enwrapped the city like a wet blanket.

The chimes in a church steeple, two blocks farther on, had just struck the hour of ten, and except for Peret and one other wayfarer, who had paused in the sickly glare of the corner lamp to light a cigarette, the street was deserted.

"A fine night for a murder!" muttered Peret to himself, as, with head lowered, he plowed his way through the fog. "Diable! I must find a taxi."

With this thought in mind, he was about to quicken his pace when, instead, he jerked himself to an abrupt halt and stood in an attitude of listening, as the tomblike silence was suddenly broken by a hoarse scream, and, almost immediately afterward, a cry of agony and terror:

"Help! help! I'm dying!"

The cry, though muffled, was loud enough to reach the alert ears of Peret. It appeared to come from a tall, gloomy-looking building on the right side of the street. By no means certain of this, however, Peret crouched behind a tree and strained his ears to catch the sound should it be repeated.

But no cry came. Instead, there was a terrific crash of breaking glass, and Peret twisted his head around just in time to see a man hurl himself through the leaded sash of one of the lower windows of the house and fall to the pavement with a thud and a groan.

A moment later Peret was by his side. Whipping out a small flash-light, he directed the little disc of light on the man's face.

"Nom d'un nom!" he cried. "It is M. Max Berjet. What is the matter, my friend? Are you drunk? Ill? Sacre nom! Speak quickly, while you can. What ails you?"

 
The man rolled from side to side, convulsively, and tore at the air with clawlike hands. To Peret, he seemed to be grappling with an invisible antagonist that was slowly crushing his life out. His face was blue and horribly distorted: his breath was coming in short, jerky gasps.

Suddenly his tensed muscles relaxed and he lay still. Unable to speak, he could only lift his eyes to Peret's in desperate appeal.

"Dame! You are a sick man, my friend," observed Peret, feeling the man's pulse. "I will run for a physician. But tell me quickly what happened to you, Monsieur."

There was an almost imperceptible movement of the dying man's froth-rimmed lips, and Peret held his head nearer.

"Now, speak, my friend," he entreated. "I am Jules Peret. You know me, eh! Tell me what is the matter with you. Were you attacked?"

"As-sas-sins," gasped the stricken man faintly.

"What?" cried Peret, excitedly. "Assassins!"

The look in Berjet's eyes was eloquent.

"Who are they?" pleaded the detective. "Tell me their names, Monsieur, before it is too late. I will avenge you. I promise you. I swear it. Quickly, Monsieur, their names—"

Berjet murmured something in a voice almost too faint to be audible.

"Dix?" questioned Peret, straining to catch the man's words. "You mean ten, eh?"

With his glazing eyes fixed on the detective, Berjet made a desperate effort to reply, but the effort was in vain. The ghost of a sigh escaped from his lips, a slight tremor shook his frame, and, with a gurgling sound in his throat, he died.

"Peste! What did he mean by that?" muttered Peret, getting to his feet. (Dix is the French word for "ten".) Did he mean he was attacked by ten assassins? The devil! It does not take an army to kill a single man."

"What’s the matter, old chap?" It was the pedestrian whom Peret had observed lighting a cigarette near the corner lamp a few minutes previously. "The old boy looks as if he had had a shot of bootlegger's private stock."

"He has been murdered," returned Peret shortly, after giving the man a keen scrutiny. Then: "Be so kind as to run to the drug store across the street and ask the druggist to send for a physician. Also request him to notify police headquarters that a murder has been committed. Have the notification sent in the name of Jules Peret. Hurry, my friend!"

Without waiting to reply, the man spun on his heel and dashed across the street. Dropping to his knees again, Peret made a hasty but thorough search of the dead man's clothing, but beyond a few stray coins in the pockets of his trousers, found nothing. As he was finishing his examination, the stranger returned, accompanied by the druggist and a physician who had chanced to be in the drug store.

Peret rose to his feet and stepped back to make room for the doctor.

"What's the trouble?" asked Dr. Sprague, a large, swarthy-faced man with a gray Vandyke beard.

"Murder, I'm afraid," replied Peret, pointing at Berjet's motionless body.

Dr. Sprague bent over the inert form of the scientist and made a brief examination.

"Yes," he said gravely, "he is beyond human aid."

"He is dead?"

"Quite."

"Can yon tell me what caused his death?"

"I cannot be positive," replied the physician, "but he bears all the outward symptoms of asphyxiation."

"Asphyxiation?" repeated Peret incredulously.

"Yes."

 
Peret's skepticism was written plainly on his face.

"But that is at variance with the dead man's last words. I was with M. Berjet when he died and there was certainly nothing in his actions to suggest asphyxiation. However—" He exhibited his card. "I am Jules Peret, a detective. The man that you have just pronounced dead is Max Berjet, the eminent French scientist. If he was murdered—and I have reason to believe that he was—the murderer has not yet had time to escape, as M. Berjet has been dead less than two minutes. It is possible, therefore, that I can apprehend the assassin if I act at once. Can you stay here with the body pending the arrival of the police?"

Dr. Sprague glanced at the detective's card and nodded, whereupon Peret, with a single bound, cleared the iron fence that inclosed the little yard in front of Berjet's house. As he landed, feet first, on the lawn, he heard Dr. Sprague give a piercing scream.

So startled was he by the unexpectedness of it that he lost his footing and fell forward on his face. Leaping to his feet, he whirled around and directed the beam from his flashlight on the physician.

Dr. Sprague, with his hands clawing the air in front of him, appeared to be grappling with an invisible something that was rapidly getting the best of him. His lips were drawn back in a snarl: his eyes seemed as if they were about to pop from his head, and bloody froth had begun to ooze between his clenched teeth and run from the corners of his mouth.

As Peret was preparing to leap back over the fence, he heard a terrible scream issue from the throat of the unknown pedestrian, and saw him throw up his arms as if to ward off a blow. Then the man reeled back against the fence and began to struggle desperately with something that Peret could not see.

Whipping out his automatic, the detective again vaulted the fence, but before he could reach either of them, both Dr. Sprague and the pedestrian crashed to the pavement, the first dead, the second still fighting for his life.