Frank Hardy swung the flashlight, and the wolf before them sprang back, snarling ferociously, into the darkness. The pattering of feet at the back of the huge cavern became more insistent. The boys were conscious of those greenish eyes all about them. The wolves were circling around the cave.

Another wolf joined the animal that barred the entrance. By some animal cunning, they seemed to realize that by so doing they could entrap their prey. The Hardy boys knew that they had wandered into a veritable den of timber wolves who had found in this abandoned mine an ideal refuge and shelter, who had probably made the place their own for years.

The wolves drew closer. The circle was narrowing. The animals were beginning to pace about the cave in long strides, drawing in toward the boys as the circumference of the circle grew smaller.

“Keep the flashlight on,” said Joe. “They’re afraid of the light.”

Frank kept turning slowly about, keeping the glare of the flash full on the circling wolves, and every time its radiance illuminated a gaunt grey form the animal would leap back, snarling, into the shadows.

But as quickly as the light was turned away from one side, the wolves on the other side of the circle would grow bolder and come closer. It was inevitable that in a few minutes the lads would be torn to pieces.

Suddenly Frank thought of the revolver they had seized from Slim Briggs. It was still in his pocket and he had forgotten all about it until this time. With his free hand he reached for the weapon.

Slowly he withdrew it. Then, turning the flashlight directly on one of the snarling beasts, he took aim and fired.

The animal dropped in his tracks with a yelp of pain, and instantly the ranks of the wolves were broken as they fled howling to the darkest corners of the cavern. The stricken wolf writhed and snarled wretchedly for a moment, then lay still.

The boys edged back toward the entrance, but before they could reach it a grey form shot across the circle of light and barred the way with a snarl of defiance. Again they were trapped. Frank fired at the animal. The shot went wide and the brute slunk back, but still remained in the passageway. Two or three of the other animals came rushing out of the darkness and pounced on the body of the dead wolf, tearing at the flesh with savage jaws. For a while the cave echoed with growls and snarls as the animals set about their hideous meal, and then the revolver crashed forth again and another wolf toppled over dead.

“Three shells left,” said Frank.

“Save them. We’ll take a chance on getting out.”

But the chance appeared to be a slim one. More wolves had joined their leader at the entrance, and it seemed impossible that the boys could ever make their escape that way.

The wolves began to advance. The leader came forward, showing his teeth. His eyes glowed like spots of green flame.

Step by step, the boys retreated.

The animals appeared to have overcome their fear of the flashlight. They no longer slunk into the shadows when its fierce glare was turned on them. Instead, they came forward boldly, with dripping, gleaming jaws.

“I’m afraid we’re trapped,” declared Frank.

“We’ll die fighting, anyway. I wish I had a gun.”

“Wouldn’t be much use against this pack.”

“Turn your flash and see if there isn’t any other way out of this place except the way we came in.”

Frank turned the light swiftly about toward the walls back of them and in the radiant gleam the boys saw a narrow passage, like a dark splotch against the rock, just a few feet away.

“That looks like our only chance.”

“We’ll try it, anyway. It seems to lead back into the wall quite a distance.”

“It may be all right⁠—as long as we don’t run into another wolf den.”

“Those brutes will follow us.”

“The whole pack can’t get into that narrow tunnel, at any rate. We’ll have a better chance of fighting them off.” Frank turned the light swiftly on the dark passage again. “You try it first. They may try to rush us when they see us getting away.”

They backed up as close to the opening in the rocks as they could. The wolves were very near now. Three of them had thrust their cruel heads directly into the circle of light from the flash. Their vicious snarling echoed throughout the cave. Frank sensed that they were preparing to spring.

“Quick!” he urged his brother.

Joe leaped and scrambled into the opening.

At the same instant the foremost wolf crouched for a spring. There was not a second to lose. Frank leveled the revolver and fired.

His aim was true. Halfway in the air the animal gave a convulsive twist of its body and crashed on to the rocks. It writhed in its death agony, snarling ferociously and snapping at everything within reach, until it finally lay still.

The respite was just what the boys needed. The other wolves slunk back, discouraged by the loss of their leader. Frank knew, however, that it would be but for a moment. He backed into the passage with Joe.

The tunnel was narrow, but high enough to permit them to move about without crouching. They were unable to light their way, as Frank needed the flashlight turned before him in order to frighten back the wolves. For a moment the animals seemed to hesitate, as though fearing a trap and then the foremost wolf cautiously entered the tunnel in pursuit of its prey.

The boys backed slowly down the tunnel, which descended on a slope. They did not know where it led, they could not see, but they knew they must keep backing away from the wolves.

“We’re up against it if this is a blind alley,” declared Joe, in a low voice.

“We’re up against it if we stop and try to fight it out.”

Step by step they moved backward, and step by step the foremost wolf pursued them.

The animal was more cowardly than the leader that had been killed. He did not advance boldly, but slunk along, pressing to the side of the tunnel as though trying to evade the dazzling gleam of light that shone in his eyes. Now and then he snarled viciously, showing his teeth.

“Are any of the wolves following him?” asked Joe, from the darkness.

“I can’t see any. This brute seems to be alone.”

“How about taking a shot at him?”

“What’s the use? Even if I did kill him, we’d only run into the rest of them when we went out into the cave again. I’m not going to use this gun again unless I absolutely have to.”

The brothers continued their weird journey. The tunnel was damp and chilly. The floor was rocky and uneven, and Frank was in constant dread lest he trip and fall. It would be all up with them then. The wolf would not lose a second in taking advantage of such an opportunity. So, stepping backward, they retreated farther and farther down the passage, watching the grey form that constantly followed, never gaining on them, but never falling back.

“I wonder how long this tunnel is?” Frank muttered.

“Can’t last forever,” said Joe, with an attempt at cheerfulness. “I think I feel a draft of cold air at my back.”

“It doesn’t lead outside, that’s certain. If it did it would be sloping upward.”

There was a low snarl from the wolf. It advanced farther into the circle of light. The brute had evidently decided that the light was not particularly dangerous, and was growing bolder.

Frank tightened his grip on the revolver. The animal was preparing for a rush.

The gaunt grey form gathered itself together and came directly at him.

Frank pressed the trigger.

The revolver crashed forth, awakening thunderous echoes in the narrow tunnel. The wolf gave vent to a howl of pain and fury, but although its onward course was checked for a moment and it swerved to one side it did not fall back. The bullet had not found a vital spot. Maddened by pain, the animal came on again.

The boys scrambled back. The wolf leaped. Frank flung himself to one side and the great body brushed against him. He struck out with the revolver and felt the weapon strike against flesh. Again he pulled the trigger, with the barrel of the weapon directly against the animal’s hide, and then he sprang farther back into the tunnel.

Behind him he heard a shout. It seemed curiously far away. He retreated another step.

His foot did not find the solid rock. Instead, he stepped back into space. For an instant he wavered, clutching vainly at the air. Then he lost his balance, staggered backward, and then felt himself falling on downward into utter darkness.