"Drop!" he rapped.

The others had only time to sag their jaws in astonishment before a short, shrill whistle knifed at their eardrums.

Every man flattened; they knew that sound. It meant the pa.s.sage of a high-powered rifle bullet. The gra.s.s was almost knee-high. p.r.o.ne in it, the men could not be seen at a distance of more than fifty feet.

"Spread out, brothers," Doc directed. "He's liable to try random shots into the gra.s.s."

"How'd you locate him, Doc?" Monk called.

Not getting an answer, Monk angled over to find Doc, with the intention of putting the question again.

But the bronze man was not to be found.

Doc, at the moment, was scores of yards away, He traveled swiftly, almost against the ground.

Another bullet made a loud buzzing sound through the gra.s.s.

Doc's discovery of the rifleman had been no accident. For the previous mile of their progress, the bronze man had noticed a marked lack of bird life. To his trained eye, this indicated some one was moving ahead of them and had frightened the feathered creatures away. Accordingly, he kept his eyes open.

He had sighted the bushwhacker's rifle as the fellow aimed.

The rifleman had a plain white handkerchief tied over his face.

Doc gained the edge of the clearing. Not until he was well into the conifers did he arise. A mighty Nemesis of bronze, he circled to flank the attacker.

He was unsuccessful. The rifle wielder, suspecting his shots had missed, had fled. He could be heard plunging through the brush.

Doc Savage, heading across to intercept the man, found his path barred by a great thicket of brambles.

Large trees grew out of the th.o.r.n.y maze. Their branches almost interlocked in spots.

Scarcely slackening his running pace, the bronze man hurtled upward in a great leap. His hands clamped a low limb, and the momentum of his leap carried him over. With an acrobatic agility he landed atop the limb, maintaining a perfect balance. He remained there so briefly, however, as to seem not to pause at all. He swung up and out, caught another limb, and repeated the process until he stood among the top-most branches.

He glided out on a bough and sprang into s.p.a.ce. An onlooker, not knowing the tremendous quality of the bronze man's muscles, would have felt he was committing suicide. Doc's hands found the branch of another tree. He went on through the aerial lanes.

His progress involved Herculean exertion, but he was probably traveling as swiftly as the fleeing rifleman.

Beyond the brambles, Doc dropped to the earth. He was on his quarry's trail. His path lead through tangled brush, through thickets of stunted evergreen.

They descended a sharp slope. A sluggish stream appeared, wide and shallow. At one point, a log had fallen across the water. The bushwhacker's trail led directly to the log.

Doc Savage reached the log and stopped.

The water beneath the log was only a few inches deep, and it overlay pleasant-looking sand. This sand was riled, disturbed.

At one point, great bubbles were rising and bursting.

QUICKSAND! AND the bubbles arising might mean some one had fallen in. Or it might mean that Doc's quarry had dropped a rock into the treacherous sand, in an effort to pull a trick.

Doc's eyes ranged the log. It was covered with a green moss. This was undisturbed. The bushwhacker had not walked across; and nowhere was the quicksand stream narrow enough to leap.

Doc gazed around. There were no limbs to which the fugitive might have sprung to hide his tracks.

The opposite bank of the stream was a wall of brush and small trees, and beyond lay thick timber. To gain refuge, the bushwhacker would have had to take wing.

The fellow was in the quicksand. No doubt of it! From Doc's clothing came the silken cord and grappling hook which he so frequently found of use. He doubled the cord twice, and took a loop around the log.

Monk and the others came up. They were scratched; their clothing was torn. Ham's immaculate garb hung in tatters. They had evidently had a tough time with the brier thicket.

"Hey, Doc!" Long Tom yelled in horror. "You ain't gonna go into that stuff, J hope!"

Doc did not reply. He knotted the ends of the silk cords around a wrist and tied them securely, allowing just enough line to prevent his arm sinking below the surface.

The giant bronze man dropped into the quicksand. As he had expected, the stuff was very loose and liquid. This accounted for the quick disappearance of the bushwhacker.

Doc churned about. He had no trouble sinking in the stuff. The difficulties would come when he sought to extricate himself.

His feet soon found a yielding form. He worked at this, and got it clamped between his knees.

Then came the laborious job of hoisting himself. It was a terrific task, even for Doc's matchless strength.Very slowly his rising was hardly perceptible to the eye -- he lifted himself and his prize.

Great tendons, which were normally part of the symmetrical mold of his arms, stood out in tremendous fashion. His arms might have been corded with steel bars. Perspiration rivulets wriggled down his bronze skin, and mixed with water which covered the quicksand.

The sand made unlovely bubbling noises. Doc's men waited on the bank above. Monk had to be restrained from wading out into the quicksand, with the idea that he might be of some a.s.sistance.

At last, Doc lifted the bushwhacker free of the quicksand. He carried the fellow out and laid him on the bank. The man's handkerchief mask was gone now.

It was Caldwell, the slayer of Carl MacBride. A knife hilt stood out from his chest.

IN A dazed fashion, the gaunt Johnny fumbled with his monocle magnifier.

"The knife -- this fellow was murdered!" he gasped. "Is he the same man who fired upon us?"

"The same," Doc replied. "Weren't there any other tracks around?"

Instead of replying, Doc stood erect and ran across the log which spanned the quicksand. He entered the thick bushes on the opposite bank. There he found the explanation of the knife in CaIdwell's heart.

Tracks! There was the print of a large foot encased in pac-type shoes. The maker of the print had stood for some time.

Doc followed the pac trail of Caldwell's killer. It was a short procedure. A hundred yards to the right, the quicksand brook joined a larger stream. The murderer had entered a canoe.

Doc worked up the stream, then down. He studied the fish, for the water was clear, trying to ascertain in which direction the finny denizens had been frightened to cover by the pa.s.sage of the canoe. It was not this, but the absence of turtles from logs, that gave him his clew. The killer had. gone downstream.

Doc set out in that direction. A low pop-pop-pop came from ahead -- an outboard motor.

Ten minutes later Doc gave it up. He could not hope to overhaul a canoe fitted with an outboard.

He rejoined his men. They had the contents of Caldwell's pockets spread out on the gra.s.s. These consisted of a penknife, cartridges for a rifle, a case of cigarettes, and a sheet of yellow paper which had evidently been torn from a grocery wrapper.

Three words were written on the paper: THE DEATH MILL.

"What in blazes do you reckon that means?" Monk demanded.

They left the body of Caldwell where it lay. As a death shroud, Monk and Ham contributed what the brier thicket had left of their coats.

It did not take them long to reach Trapper Lake.

"Not such a hot-lookin' town," Monk decided.

Changing the subject impolitely, Ham pondered aloud, "But why was Caldwell murdered?" "Probably because we knew his ident.i.ty," Doc replied.

"But he was masked when he shot at us."

"We saw his face when he killed Carl MacBride in New York," Doc reminded. "That made him a liability to his gang. He was a definite individual for whom we could hunt."

"Wonder if Pere Teston killed hi," pale Long Tom muttered thoughtfully.

Doc did not reply.

They worked their way through the business section of Trapper Lake. This was spread along a single street.

Doc entered a general store. In slightly over a minute, he was outside again.

"You fellows wait here," he directed.

Ham waved his sword cane. "But what -- "

He withheld the rest. Doc Savage had already vaulted a wooden fence and set out across lots.

In the general store, Doc had asked about a spot called The Death Mill. This place, it seemed, was an old grist mill on the outskirts of town. The ominous place had been deserted for years, it seemed, ever since the former owner had been caught in the grinding stone and crushed to death. Hence the name -- The Death Mill.

Doc sighted the dilapidated structure. Mischievous boys had knocked planks off the walls; the roof had shed shingles, as if it had the mange.

Doc took to roadside brush as he drew near. He circled the mill warily, for he could hear sounds from within -- nervous pacing.

A man came to the ramshackle door and stood looking out. It was fat Griswold Rock, who had vowed he was on his way to Europe when Doc had last seen him!

Chapter 17. RENNY's MYSTERY MISSION.

DOC SAVAGE bobbed into view.

For a fat man, Griswold Rock moved suddenly. He jumped at least a foot in the air. He leaped backward, and his head, due to his own clumsiness, banged the ancient door jamb. He sank to his knees, half stunned.

He began to tremble. The trembling was an interesting phenomenon, for it made all of his fatty bulges seem to be tilled with kicking frogs. It was almost a minute before he controlled himself.

"I'm so g-g-glad you've come," he stuttered.

Doc's bronze features exhibited no change of expression. "Your t-t-telegram s-said you'd be here ab-bout this t-time," continued Griswold Rock, still stuttering.

"Telegram!"

"The one you sent me in New York. I got it just as I was ready to leave for Europe." "I sent you no telegram!"

Griswold Rock had gotten to his feet At the words, his knees buckled as if the tendons had been cut. In his distress, his fingers seemed to wriggle separately, like fat living strings.

"The t-telegram t-told me to come here and w-wait," he wailed. "It was s-signed with your name. Do you think it was a t-trap to rn-murder me?"

Instead of answering, Doc Savage roved his gaze over the surroundings. The weeds were very tall, the brush rank; vines entwined to make a labyrinth. Somewhat scrawny-looking walnut trees thrust above the whole. It was a macabre place, suggesting rattling chains and ghostly cries.

"There are no tenanted dwellings near by," Doc reminded.

Griswold Rock tied his hands into a fatty lump. "They decoyed me here. Maybe they planned to seize me again. Worse still, they might have intended to kill me."

Doc Savage entered the abandoned mill and moved through its moldy rooms. He even examined the cracked, long-disused grinding stones in which the former operator had met his death.

Dust was thick. That made it simple -- for the bronze man's trained eyes -- to ascertain that no one but Griswold Rock had visited the place recently.

"Where is the telegram which you received?" Doc asked.

"I took a room in the Guide's Hotel," explained Griswold Rock. "I left the wire there."

"Let's go have a look at it."

The backwoods nature of Trapper Lake was evident as they made their way through the streets.

Wooden planks were evidently cheaper than concrete, and most of the sidewalks were composed of this material.

The residents were robust, friendly souls. Although Doc Savage and Griswold Rock were strangers, they received pleasant greetings.

The Guide's Hotel, in addition to being the largest building in town, was the newest. It was entirely of frame construction.

The two men went directly to a room on the second floor. Griswold Rock opened his suitcase.

"Oh, my!" he wailed. "It's gone! Somebody's taken the telegram!"

Doc Savage left the room and descended the stairs. He found the hotel proprietor.

"Have you noticed any one prowling around within the last few hours?" he asked.

"Within the last two hours," amended Griswold Rock, who had followed Doc. "I just arrived here two hours ago. I came most of the distance from New York by plane."

The Guide's Hotel proprietor was a grizzled man with humor in his eyes.