Halfway up, the motor coughed and died. Stoner swore and set his brakes. It was what The Shadow had expected. He knew now what was coming.

"The gas gauge fooled me," Stoner said, thickly. "The tank must be empty.

I thought I had plenty for the trip."

He grinned, shrugged.

"Do you mind getting out and looking? There's an extra gallon tin in the trunk carrier on the back. Fill the tank, while I watch the brakes, will you?

This is a bad hill to stop on."

The Shadow nodded. He got out slowly, walked wheezingly to the back of the stalled car. But the moment he was out of sight of the driver, his movements became rapid.

He paid no attention to the gas or the cap. He lifted the trunk cover.

There was an extra tin of gas inside - and something else that made his eyes gleam. An empty, leather suitcase!

Noiselessly, he laid the suitcase on the road behind the left rear tire.

Then he unscrewed the tank cap, making plenty of noise. The next instant he was flat on the ground, his body as straight as an arrow between the wheels. His arms and legs were stiffly extended, his face pressed sidewise, as close as he could bring it to the earth.

He had barely flung himself into this flattened position when the brakes of the stalled car were suddenly released.

THE heavy automobile rolled swiftly backward, crunching over the suitcase.

The Shadow gave a shrill, agonized scream that choked into silence.

Speeding backward down the steep bill, Stoner felt the crunch under the wheels. He saw two motionless objects emerge on the road in front of the car.

He braked to a jarring standstill. He had extinguished his lights. But in the gloom he could see dimly the limp body of his late pa.s.senger. There was another object close to the old man, which the trembling Stoner couldn't identify. He got out of the car, walked slowly toward his victim. He was still a half dozen paces away when he recognized the battered suitcase. He saw that the old man was unhurt. With a shrill oath of dismay, he realized what had happened, and his hand jerked a pistol from his hip.

The Shadow's drawn gun was under his left elbow. He fired instantly and his bullet pierced Stoner's arm, dropping it limp and releasing the gun from Stoner's stiffened fingers.

Before Stoner could clutch with his free hand, The Shadow was on him in a silent attack that reduced his foe to a helpless huddle. A light, strong cord from beneath The Shadow's coat swathed the would-be murderer like a mummy. A handkerchief was jammed into the clenched jaws.

In another instant, Stoner was tossed into the car and The Shadow was behind the wheel, backing swiftly down the long hill. He turned the automobile around and returned to the side lane in the road with a quick burst of speed.

The gas tank, of course, was not empty; that had been merely Stoner's lying excuse for a planned murder.

A quarter of a mile into the property of the mysterious Mr. Fox, and the winding lane came to an end. Beyond it was a small footpath winding to the left between thick, overhanging bushes. The Shadow parked the car out of sight, made sure Stoner was taut and helpless, and hurried on foot along the path.

The path ended in an enormous weed grown hole in the dark earth. The vertical edges of rotted supporting timbers showed like broken teeth. It was the unkempt and decayed entrance to an old and abandoned iron mine!

The Shadow's flashlight glowed with steady brilliance. It threw a small circle of vivid light ahead of him. The white wig and mustache of the old man were now gone. Once more, The Shadow was robed in black.

He entered the mine.

CHAPTER XXII.

SINISTER LAKE.

INSIDE the brand-new sedan that was hidden under interlaced boughs at the end of the private lane, David Stoner tried grimly with his uninjured arm to escape from his bonds. It was useless. He could neither stir nor cry out.

Suddenly, he ceased his desperate efforts to release himself. He had heard a clear warning whistle: a peculiar double note like a thrush. It was instantly repeated.

An ugly-looking man in soiled dungarees had given that warning signal. He had moved furtively into view from a direction exactly opposite to that taken by The Shadow. There was a flashlight in his hand and he sent its rays impatiently along the ground. He had expected to meet Stoner at this very spot, and Stoner wasn't here.

Suddenly, his eyes narrowed with suspicion. He had seen the tire marks in the lane. The beam of his torch swept inward toward the bunched trees. He saw the ruddy reflection of an automobile's tail-light. The light was out; the glow was merely a reflection. In a moment, the man in dungarees was advancing cautiously, a gun in his hairy, soiled hand.

He discovered Stoner's predicament, released him, helped him to his feet.

The moment the gag was out of Stoner's jaws, he began to whisper fierce, impatient sentences. The man in dungarees listened with respectful attention. "Quick!" Stoner gasped. "You'll have to give me a hand, get me down that rope in a hurry! There's not a minute to lose!"

He turned, ran, and the thug at his side ran with him. They hurried in the same direction from which the thug had so mysteriously appeared. Their route took them away from the mine entrance. They approached a cliff and halted at its very edge. The edge dropped away sixty or seventy feet to the rocky, weed-grown bottom of a precipitous ravine.

Peering over the edge, Stoner gave a croak of satisfaction and impatience.

There was a stout, knotted rope attached to a metal hook imbedded in the rock.

The rope dangled about twenty-five feet to a small isolated ledge on the face of the cliff.

"Can you get me down without losing your grip?" Stoner snarled.

"Sure thing!"

"All right. Let's go!"

It was slow and ticklish, but the man in dungarees was as good as his boast. Stoner wound his uninjured arm about the neck of his henchman. His legs were wrapped tightly around the man's thighs and he hooked his toes together as an added brace.

The two men vanished over the sheer edge of the rocky wall. They descended inch by inch, the hands of the man in dungarees moving jerkily from knot to knot in the lifeline.

He was panting, covered with sweat, when they reached the ledge. But Stoner gave him no chance to recover his breath.

"Come on! I've got to get that siren blowing!"

BOTH of them now held small flashlights. The light streamed through a small opening in the cliff, disclosing an ancient-looking tunnel. This was one of the abandoned galleries of the iron mine owned by the elusive Mr. Fox.

The two panting criminals hurried along the narrow pa.s.sage, crouching in places where the roof was low. They came presently to a huge boulder, that blocked further progress.

But the man in dungarees jerked a lever in the wall and the boulder rolled aside, returning to its position after they had pa.s.sed. They were now in a more modern gallery. It was lined with smooth concrete and spotlessly clean. It led in a gradual slant, turning occasionally till it reached another barrier.

This was something quite different from the boulder they had left far behind them. It was the steel door of a modern elevator shaft.

Stoner pressed a b.u.t.ton and the steel door slid aside, disclosing a small elevator into which both men hurried. There were only two b.u.t.tons on the panel at the side. Stoner pressed the lower one. Immediately, the car began to descend. It dropped to a considerable depth. Then it halted and the door opened, automatically.

The pa.s.sage beyond was hewn from virgin rock and it was not very long in extent. It opened into a tremendous underground chamber - if "chamber" could adequately describe it. Electric lamps, strung overhead on stout wires, illuminated dimly a huge cavernous opening in the bowels of the earth.

The light was reflected like stars from the dark, uneasy glimmer of the surface of an underground lake.

There was an empty rowboat drawn up on the muddy sh.o.r.e of this black expanse of underground water. A pair of oars lay alongside. They were dripping wet, showing they had been recently used.

Stoner's companion shoved the boat into the water, steadied the craftwhile Stoner climbed aboard. Then he began to row swiftly across the underground lake, following the glow of the electric lights strung overhead in the rocky roof of this immense chamber.

The crossing took ten minutes of steady pulling. The sh.o.r.e on the opposite side sloped steeply downward from the water. The lake ended in a cement retaining wall that kept the water from overflowing its basin and spilling down the steep declivity beyond.

The two men moored the rowboat and hurried down the dark, rocky slope to what appeared to be the end of the mine - a barrier of solid iron-ore cliff, shining faintly in the dim light. But there was a way through. A steel door was sunk flush with the surface of the rock.

Stoner turned, pointed along the wall to a fissure in which was visible the steel rungs of a vertical ladder. The man in dungarees ran to the ladder and climbed upward, vanishing into the gloom at the top.

Stoner did not follow. His trembling left hand produced a key, unlocked the steel door in front of him. He pa.s.sed through, and the door swung shut behind him.

There was no clang of metal. The edges of this strange door were faced with rubber - soft, spongy and watertight.

A moment or two pa.s.sed, then the door opened again. It stayed open, waiting ominously, for the expected arrival of The Shadow. The final and most deadly trap of Foxhound was ready. It was baited with the bound and helpless bodies of two men and a woman.

CRAWLING slowly along in the ancient entrance to the mine, The Shadow soon discovered that he had made a serious blunder. The weed-choked pa.s.sage became narrower and narrower. It became obvious to him that the pa.s.sage had not been used by human beings for years past. He had allowed the desperate need for haste to cloud his judgment.

He rectified that error at once. Squirming about, he crawled back to a spot where he could stand erect. He hastened once more to the surface of the ground. He retraced his steps to the spot where he had concealed the car that contained Stoner.

A glance at the earth as he approached, and he knew Stoner had already made his escape. He saw the marks of footprints in the spongy ground: the trail of two men. In order to satisfy himself that it was not a deliberate trap to capture him, he approached the hidden car stealthily, peered inside. It was empty.

The Shadow followed the footprints. No attempt had been made by the fugitive pair to conceal them. On the contrary, they made a clear, well-defined trail. The Shadow made an instant deduction from this fact. Stoner and his rescuer wanted him to follow them.

Grimly he obliged. The trail led him straight to the edge of a steep cliff. His movements became slower now, more cautious.

He climbed down the knotted rope to the ledge below, entered the gallery of the mine. Inside, the boulder that had rolled aside for Stoner did the same thing for The Shadow. It was impossible not to see the lever in the wall that operated it. Again, no effort had been made to camouflage it.

Down this newer, more modern concrete gallery The Shadow hurried, straight to the elevator shaft. The lift took him down into the depths of the earth. He came at last to the huge cavern of the underground lake.

A faint exclamation of wonder came from the tight lips of The Shadow.Foxhound must have spent a fortune arranging this snug retreat far in the bowels of the earth! No wonder he could hide with impunity from the police when the occasion arose!

The air in the cavern was fresh and clean, undoubtedly pumped from above ground. The lights strung across the black water indicated a powerful dynamo somewhere. But what of Foxhound? He knew The Shadow had, by this time, pierced his secret. He was bent on luring The Shadow deeper and deeper into the earth.

But where?

The answer was clearly shown in the muddy sh.o.r.e of the lake. A rowboat had been launched recently from this very spot. It had crossed the lake guided by the dim, spa.r.s.ely hung lights overhead.

THE SHADOW produced twin guns. Removing his cloak, he wrapped the weapons securely and tied the compact bundle above his shoulders and back of his head.

He waded into the lake and began to swim, keeping his head high in the water.

His arms beneath the surface made no splash; nor did his submerged feet.

He swam away from the dim line of lights crossing the roof of the chamber. The water was cold, clammy and apparently alive with fish. Something wriggly and slimy gripped his ankle with a sudden pressure, but The Shadow kicked strongly and the thing let go.

He was more than halfway across the mysterious lake when he stopped swimming suddenly. He had heard the cautious splash of oars! A moment later, he saw a distant rowboat and recognized its occupant. The man was Alonzo Kelsea and he was rowing with desperate haste.

The Shadow, treading water with calm efficiency, was utterly invisible from the man in the boat. Nor would Kelsea have seen him in any event; for at this moment a weird shriek filled the mine with a blood-curdling and screaming clamor.

It was an electric siren! Its grim blast seemed to be a warning for Kelsea to hurry.

Kelsea redoubled his anxious efforts at the oars and landed at the concrete wall that lined the opposite sh.o.r.e. He ran, as Stoner had run before him, down the steep declivity that led to the steel door in the rock. He ran past the door and ascended the rungs of the vertical ladder in the fissure of the wall.

The Shadow was too far out in the lake to tell accurately just where he had disappeared. One moment he was vaguely visible; the next, he was gone.

The Shadow knew there was no time to waste. He was aware that the lives of at least three people depended on his speed and his intelligence. His powerful stroke pulled him to the edge of the lake. He approached the steel door. It was partly open, as though someone had forgotten to close it.

The Shadow knew that the open door was not chance. Crouched in the darkness, he eyed the door and the vertical steel ladder in a fissure just beyond. The Shadow crept, not toward the ladder, but toward the door.

He peered in.

THE sight that greeted The Shadow froze him into attentive caution. Two men and a woman were bound and gagged on the stone floor of the chamber. Their bodies stretched outward like triple hands of a clock from a heavy chunk of iron ore to which their feet were securely tied.

The girl was Madge Payne. One of the men was Doctor Bruce Hanson. Theother was Joe Cardona.

It was Joe who saw The Shadow first. His eyes bulged with a fierce, terrified warning. His head shook a violent "No!"

His meaning was as clear as though he had yelled desperately at the top of his lungs: "Forget us! Keep out! It's a trap to lure you to death with us!"

The Shadow knew now that this was the spot where Jimmy Dawson had been drowned. He remembered how the earth slanted so steeply downward from the concrete wall of the lake. He saw three things in the chamber that confirmed his opinion. One was the chunk of iron ore to weigh down the victims. The other two were circular metal plates in the floor and the ceiling of the vault-like room.

The Shadow eyed the size of the chunk of ore. He observed the diameter of the circular plate in the floor.

Then, deliberately, he entered the trap that Foxhound had prepared for him and three others. The rubber-sheathed door slammed behind him the moment he had pa.s.sed the threshold.

CHAPTER XXIII.

THE SECRET OF FOXHOUND.

A QUICK slash of The Shadow's knife released the three victims. Cardona rolled weakly to his knees, jerked the gag from his mouth.

"Too late!" he gasped.

"Exactly! Too late, as Mr. Cardona so aptly says."

The voice was cold, metallic, filled with murderous amus.e.m.e.nt. It issued from the circular opening in the ceiling of the stone room. The watertight plate above had lifted. But there was no face in the opening. Foxhound was lurking cautiously out of sight.