Around the turn of the tunnel, approaching the vault apparently from another passage, they heard hurrying footsteps; and then, close to them from the vault itself, the voice of Professor Peabody.

It was harsh, sharp, peremptory.

"Hands up!" it commanded. "Drop that gun!"

As though halted by a precipice, the footsteps fell into instant silence. There was a pause, and then the ring of steel upon the stone floor. There was another pause, and Monica heard the voice of her brother. Broken, as though with running, it still retained its level accent, its note of insolence.

"So," it said, "I have caught you?"

Monica struggled toward the lighted vault, but around her Everett threw his arm.

"Come away!" he begged.

Monica fought against the terror of something unknown. She could not understand. They had come only to prevent a meeting between her brother and Peabody; and now that they had met, Everett was endeavoring to escape.

It was incomprehensible.

And the money in the vault, the yellow bills hanging from a cobweb of strings; why should they terrify her; what did they threaten? Dully, and from a distance, Monica heard the voice of Peabody.

"No," he answered; "I have caught you! And I've had a hell of a time doing it!"Monica tried to call out, to assure her brother of her presence.

But, as though in a nightmare, she could make no sound. Fingers of fear gripped at her throat. To struggle was no longer possible.

The voice of Peabody continued:

"Six months ago we traced these bills to New Orleans. So we guessed the plant was in Central America. We knew only one man who could make them. When I found you were in Amapala and they said you had struck 'buried treasure'--the rest was easy."Monica heard the voice of her brother answer with a laugh.

"Easy?" he mocked. "There's no extradition. You can't touch me.

You're lucky if you get out of here alive. I've only to raise my voice--""And, I'll kill you!"

This was danger Monica could understand.

Freed from the nightmare of doubt, with a cry she ran forward.

She saw Peabody, his back against a wall, a levelled automatic in his hand; her brother at the entrance to a tunnel like the one from which she had just appeared. His arms were raised above his head.

At his feet lay a revolver. For an instant, with disbelief, he stared at Monica, and then, as though assured that it was she, his eyes dilated. In them were fear and horror. So genuine was the agony in the face of the counterfeiter that Everett, who had followed, turned his own away. But the eyes of the brother and sister remained fixed upon each other, hers, appealingly; his, with despair. He tried to speak, but the words did not come. When he did break the silence his tone was singularly wistful, most tenderly kind.

"Did you hear?" he asked.

Monica slowly bowed her head. With the same note of gentleness her brother persisted:

"Did you understand?"

Between them stretched the cobweb of strings hung with yellow certificates; each calling for five hundred dollars, payable in gold.

Stirred by the night air from the open tunnels, they fluttered and flaunted.

Against the sight of them, Monica closed her eyes. Heavily, as though with a great physical effort, again she bowed her head.

The eyes of her brother searched about him wildly. They rested on the mouth of the tunnel.

With his lowered arm he pointed.

"Who is that?" he cried.

Instinctively the others turned.

It was for an instant. The instant sufficed.

Monica saw her brother throw himself upon the floor, felt herself flung aside as Everett and the detective leaped upon him; saw her brother press his hands against his heart, the two men dragging at his arms.

The cavelike room was shaken with a report, an acrid smoke assailed her nostrils. The men ceased struggling. Her brother lay still.

Monica sprang toward the body, but a black wave rose and submerged her. As she fainted, to save herself she threw out her arms, and as she fell she dragged down with her the buried treasure of Cobre.

Stretched upon the stone floor beside her brother, she lay motionless.