The two rodentlike men now retreated a pace. They were excited. A trembling racked their bony, starved hands. Nervous swallowing chased the Adam’s apples up and down their stringy necks. The rough, unwashed skin of those necks gave them a turtle aspect.

Squint dived an emaciated claw inside his shirt. The hand clutched convulsively and drew out a strange pistol. This was larger even than a big army automatic. It had two barrels, one the size of a pencil, the other a steel cylinder more than an inch in diameter. The barrels were placed one above the other.

At prone Jerome Coffern’s chest, Squint aimed the weapon.

"H-hurry up!" stuttered his companion. The man twitched uneasy glances over the adjacent shrubbery. No one was in sight.

Squint pulled the trigger of the strange pistol. It made a report exactly like a sharp human cough.

An air pistol!

That accounted for the two barrels, one of which, the larger, was in reality the chamber which held the compressed air that fired the gun.

The missile from the air pistol struck the center of Jerome Coffern’s chest.

Instantly a puff of grayish vapor arose. It was as though a small cloud of cigarette smoke had escaped from the chemist’s body at that point.

No sound of an explosion accompanied the phenomena, however. There was only the dull impact of the air gun missile striking.

The grayish vapor increased in volume. It had a vile, oily quality. Close to Jerome Coffern’s body, it was shot through and through with tiny, weird flashes. These were apparently of an electrical nature.

It was as though a small, foul gray thundercloud were forming about the distinguished chemist’s dead body.

About two minutes passed. The repulsive gray fog increased rapidly. It was now like a ball of ash-colored cotton twelve feet thick. From the ground upward about half way, the green and blue and white of the electric sparks played in fantastic fashion.

The whole thing was eerie. It would have baffled a scientific brain.

The balmy spring breeze, whipping along the narrow concrete path, wafted the vile gray cloud to one side.

Both ratty men stared at the source of the cloud.

"It’s w-w-workin’!" whined Squint. Stark awe had gripped him. He hardly had the courage to look a second time at the source of the gray vapor.

For Jerome Coffern’s body was dissolving!

THE ghastly melting-away effect had started where the mysterious missile from the air pistol had struck.

In all directions from the point of impact, the form of the great chemist was literally turning into the vile grayish vapor. Clothing, skin, flesh and bones — everything was going.

Nor did the dissolution stop with the human body. The concrete walk immediately below was becoming ashen vapor as well. The trowel-smoothed upper surface of the walk was already gone, revealing the coarse gravel below. As by magic, that, too, was wafted away. Rich black earth could be seen.

In the midst of the weird phenomenon glistened a bit of shiny metal. This resembled the crumpled tinfoil wrapper from a candy bar. It alone was not dissolving.

"Let’s get outa here, Squint!" whined one of the ratty men. It was obvious from the man’s manner that he was getting his first glimpse of the terrible weapon in their possession.

A substance with the power to dissolve all ordinary matter as readily as a red-hot rivet turns a drop of water into steam!

"Aw, whatcha scared of?" sneered Squint. He pointed a skinny talon at the spot where the iron pipe bludgeon had reposed on Jerome Coffern’s chest. "Only thing around here that had our finger prints on it was that pipe. And it’s gone up in smoke."

"I ain’t s-scared!" disclaimed the other, trying to snarl bravely. "Only we’re two saps to hang around here!"

"Maybe you’re right at that," Squint agreed.

With this, the two men fled. The alacrity with which Squint dived into the shrubbery showed he was every bit as anxious as his companion to quit the spot.

Hardly had they gone when the vaporizing of Jerome Coffern’s body abruptly ceased. It was apparent that the hideous power of the weird dissolver substance had been exhausted. Only a small quantity could have been contained in the air-pistol cartridge. Yet its effect had been incredible.

Of Jerome Coffern’s form, a right hand and forearm remained intact. This right arm had been outflung when the chemist fell after being knocked unconscious. The potency of the dissolver had been exhausted before it reached the hand and forearm. The two ratty men had fled before they noticed this.

On that grisly right wrist was the expensive watch Doc Savage had given Jerome Coffern as a token of gratitude.

The grayish vapor climbed upward in the air like smoke. And like smoke it slowly dispersed.

DOC SAVAGE, seated in his large and powerful roadster, saw the cloud of grayish vapor lift above the landscaped shrubbery.

Although it was sixty yards distant, his sharp eyes instantly noted an unusual quality about the vapor. It did not resemble smoke, except in a general way.

But at the moment Doc was doing a problem of mathematics in his head, an intricate calculation concerning an advanced electrical research he was making.

The problem would have taxed the ability of a trained accountant supplied with the latest adding machines, but Doc was able, because of the remarkable efficiency of his trained mind, to handle the numerous figures entirely within his head. He habitually performed amazing feats of calculus in this fashion.

Hence it was that Doc did not investigate the cloud of ash-hued fog at once. He finished his mental problem. Then he stood erect in the roadster.

His keen eyes had discerned the play of tiny electric sparks in the lower part of the cloud! That jerked his attention off everything else. Such a thing was astounding.

The rumble of machinery in the nearby manufacturing plant of the Mammoth concern blotted out whatever conversation or sounds which might have arisen in the neighborhood of the weird fog.

Doc hesitated. He expected his old friend, Jerome Coffern, to appear momentarily. There was no sign of the eminent chemist, however.

Doc quitted the roadster. His movements had a flowing smoothness, like great springs uncoiling in oil.

The grounds of the manufacturing plant were surrounded by a stout woven wire fence. This was more than eight feet high and topped off with several rows of needle-sharp barbs. Its purpose was to keep out intruders. A gate near by was shut, secured by a chain and padlock. No doubt Jerome Coffern had carried a key to this.

Doc Savage approached the fence, running lightly.

Then a startling thing happened.

It was a thing that gave instant insight into Doc Savage’s physical powers. It showed the incredible strength and agility of the bronze giant.

For Doc Savage had simply jumped the fence. The height exceeded by more than two feet the world record for the high jump. Yet Doc went over it with far more ease than an average man would take a knee-high obstacle. The very facility with which he did it showed he was capable of a far higher jump than that.

His landing beyond the fence was light as that of a cat. His straight, fine bronze hair was not even disturbed.

He went toward the strange gray cloud. Coming to a row of high shrubs, his bronze form seemed literally to flow through the leaves and branches. Not a leaf fluttered; not a branch shook.

It was a wonderful quality of woodcraft, and Doc did it instinctively, as naturally as a great jungle cat. It came easier to him than shoving through the bushes noisily, this trick he had acquired from the very jungle itself.