Marable and Betty were admitted, after they had pushed their way to the doors.

"Museum's closed to the public, sir," replied a guard to Marable's question.

"Why?" asked Marable.

"Somethin's happened up in the paleontological laboratories," answered the guard. "Dunno just what, but orders come to clear the rooms and not let anybody in but members of the staff, sir."

Marable hurried forward. Betty was at his heels. "Please get yourself a gun," she said, clutching his arm and holding him back.

"All right. I'll borrow one from a guard."

He returned to the front doors, and came back, slipping a large pistol into his side pocket.

"I want you to wait here," he said.

"No. I'm going with you."

"Please," he said. "As your superior, I order you to remain downstairs."

The girl shrugged. She allowed him to climb the stairs to the first floor, and then she hurried back in search of Smythe.

Smythe obtained a gun for her, and as she did not wish to wait for the slow elevator, she ran up the steps. Smythe could not tell her definitely what had occurred in the upper laboratory that had caused the museum to be closed for the day.

Her heart beating swiftly, Betty Young hurried up the second flight of stairs to the third floor. A workman, whom the girl recognized as a manual laborer in the paleontological rooms, came running down, pa.s.sing her in full flight, a look of abject terror on his face.

"What is it?" she cried.

He was so frightened he could not talk logically. "There was a black fog--I saw a red snake with legs--"

She waited for no more. A pang of fear for the safety of Marable shot through her heart, and she forced herself on to the top floor.

Up there was a haze, faintly black, which filled the corridors. As Betty Young drew closer to the door of the paleontological laboratories, the mist grew more opaque. It was as though a sooty fog permeated the air, and the girl could see it was pouring from the door of the laboratory in heavy coils. And her nostrils caught the strange odor of fetid musk.

She was greatly frightened; but she gripped the gun and pushed on.

Then to her ears came the sound of a scream, the terrible scream of a mortally wounded man. Instinctively she knew it was not Marable, but she feared for the young professor, and with an answering cry she rushed into the smoky atmosphere of the outer laboratories.

"Walter!" she called.

But evidently he did not hear her, for no reply came. Or was it that something had happened to him?

She paused on the threshold of the big room where were the amber blocks.

About the vast floor s.p.a.ce stood the numerous ma.s.ses of stone and amber, some covered with immense canvas shrouds which made them look like ghost hillocks in the dimness. Betty Young stood, gasping in fright, clutching the pistol in her hand, trying to catch the sounds of men in that chamber of horror.

She heard, then, a faint whimpering, and then noises which she identified in her mind as something being dragged along the marble flooring. A m.u.f.fled scream, weak, reached her ears, and as she took a step forward, silence came.

She listened longer, but now the sunlight coming through the window to make murky patches in the opaque black fog was her chief sensation.

"Walter!" she called.

"Go back, Betty, go back!"

The mist seemed to m.u.f.fle voices as well as obscure the vision. She advanced farther into the laboratory, trying to locate Marable. Bravely the girl pushed toward the biggest amber block. It was here that she felt instinctively that she would find the source of danger.

"Leffler!" she heard Marable say, almost at her elbow, and the young man groaned. The girl came upon him, bending over something on the floor.

She knelt beside him, gripping his arm. Now she could see the outline of Leffler's body at her feet. The wealthy collector was doubled up on the ground, shrivelled as had been Rooney. His feet, moving as though by reflex action, patted the floor from time to time, making a curious clicking sound as the b.u.t.tons of his gray spats struck the marble.

But it was obvious, even in the murky light, that Leffler was dead, that he had been sucked dry of blood.

Betty Young screamed. She could not help it. The black fog choked her and she gasped for breath. Leaving Marable, she ran toward the windows to throw them open.

The first one she tried was heavy, and she smashed the gla.s.s with the b.u.t.t of the gun. She broke several panes in two of the windows, and the mist rolled out from the laboratory.

She started to return to the side of Marable. He uttered a sudden shout, and she hurried back to where she had left him, stumbling over Leffler's body, recoiling at this touch of death.

Marable was not there, but she could hear him nearby.

Cool air was rushing in from the windows, and gradually the fog was disappearing. Betty Young saw Marable now, standing nearby, staring at the bulk of an amber block which was still covered by its canvas shroud.

Though not as large as the prize exhibit, this block of amber was large and filled many yards of s.p.a.ce.

"Betty, please go outside and call some of the men," begged Marable.

But he did not look at her, and she caught his fascinated stare.

Following the direction of his gaze, the girl saw that a whisp of smoky mist was curling up from under the edge of the canvas cover.

"It is there," whispered Betty.

Marable had a knife which he had picked up from a bench, and with this he began quietly to cut the canvas case of the block, keeping several feet to each side of the spot where the fog showed from beneath the shroud.

Marable cut swiftly and efficiently, though the cloth was heavy and he was forced to climb up several feet on the block to make his work effective. The girl watched, fascinated with horror and curiosity.

To their ears came a curious, sucking sound, and once a vague tentacle form showed from the bottom of the canvas.

At last Marable seized the edge of the cut he had made and, with a violent heave, sent the canvas flap flying over the big block.

Betty Young screamed. At last she had a sight of the terrible creature which her imagination had painted in loathing and horror. A flash of brilliant scarlet, dabbed with black patches, was her impression of the beast. A head flat and reptilian, long, tubular, with movable nostrils and antennae at the end, framed two eyes which were familiar enough to her, for they were the orbs which had stared from the inside of the amber block. She had dreamed of those eyes.

But the reptile moved like a flash of red light, though she knew its bulk was great; it sprayed forth black mist from the appendages at the end of its nose, and the crumpling of canvas reached her ears as the beast endeavored to conceal itself on the opposite side of the block.