"There are wavy lines leading around back of the block," said Marable, in answer to their questions.

The young man disappeared behind the block, and then he called to them excitedly to join him. Betty Young pressed closer, and finally slipped past the corpse and stood by her father.

Before her, she saw a large pool of black liquid. It had been hidden by the corner of the block, so that they had not noticed it, so busy were they looking at Rooney.

And there was a great cavity in the heart of the amber block. Pieces of the yellow brown ma.s.s lay about, as though they had fallen off and allowed the inky substance to escape.

"It's hardened or dried out in the air," said Young.

"It looks like black lacquer," said Betty.

The musky smell was stronger here. The great amber block seemed to stifle them with its size.

"Our chipping and hammering and the heat of the radiator causing it to expand must have forced out the sepia, or whatever it is," said Young.

There was a disappointed note in his voice "I had hoped that inside the liquid we would discover a fossil of value," he went on.

Marable looked at Betty Young. They stared at one another for some seconds, and both knew that the same thought had occurred to the other.

The frightful eyes--had they then been but figments of the imagination?

Marable began looking around carefully, here and there. Betty realized what he was doing, and she was frightened. She went to his side. "Oh, be careful," she whispered.

"The giant block has been moved a little," he replied, looking into her pretty face. "Have you noticed that?"

Now that she was told to look, she could see the extremely heavy amber block was no longer in the position it had been in. Marks on the floor showed where it had been dragged or shifted from its original resting place.

Betty Young gasped. What force could be so powerful that it could even budge so many tons? A derrick had been used, and rollers placed under the block when men had moved it.

Reason tried to a.s.sert itself. "It--it must have exploded. That would cause it to shift," she said faintly.

Marable shrugged. His examination was interrupted by the arrival of the museum's chemist, sent for by Young. The chemist took a sample of the black liquid for a.n.a.lysis. Reports were coming in from all over the museum, different departments declaring, one after another, that nothing had been disturbed or stolen from their sections.

Betty Young went again to Marable's side. She followed the direction of his eyes, and saw long, clawlike marks on the floor, radiating from the sepia.

"Doctor Marable," she said, "please don't--don't look any longer. Leave this terrible place for the day, anyway, until we see what happens in the next twenty-four hours."

He smiled and shook his head. "I must make a search," he replied. "My brain calls me a fool, but just the same, I'm worried."

"Do you really think ...?"

He nodded, divining her thought. The girl shivered. She felt terror mounting to her heart, and the matter-of-fact att.i.tudes of the others in the great laboratory did not allay her fears.

Rooney's body was removed. The place was cleaned up by workmen, and Marable's search--if that was what his constant roving about the laboratory could be called--ceased for a time. The chemist's report came in. The black liquid was some sort of animal secretion, melonotic probably.

In spite of the fact that they had learned so many facts about the murder, they as yet had not solved the mystery. Who had murdered Rooney, and why? And where had his blood gone to? In no other rooms could be found any traces of a struggle.

"If you won't do anything else, please carry a gun," begged Betty of Marable. "I'm going to try to take father home, right after lunch, if he'll go. He's so stubborn. I can't make him take care. I've got to watch him and stay beside him."

"Very well," replied Marable. "I'll get a revolver. Not that I think it would be of much use, if I did find--" He broke off, and shrugged his broad shoulders.

Leffler came storming into the room. "What's this I hear?" he cried, approaching Marable. "A watchman killed in the night? Carelessness, man, carelessness! The authorities here are absurd! They hold priceless treasures and allow thieves to enter and wreak their will. You, Marable, what's all this mean?"

Leffler was angry. Marable looked into his red face coolly. "We do the best we can, Mr. Leffler," he said. "It is unlikely that anyone would wish to steal such a thing as that block of amber."

He waved toward the giant ma.s.s.

Leffler made a gesture of impatience. "It cost me many thousands of dollars," he cried.

"It is time for lunch, Professor," said Betty.

Marable bowed to Leffler and left the millionaire sputtering away, inspecting the various specimens he had contributed.

The one o'clock gong had struck, and all the workers and investigators were leaving in paleontological laboratories for a bite to eat.

Marable, with Betty, went out last. Leffler was over in one corner of the room, hidden from their sight by a corner of an amber block. They could hear Leffler still uttering complaints about the carelessness of the men in charge of that section of the museum, and Marable smiled at Betty sadly.

"Poor Rooney," he said. "Betty, I feel more or less responsible, in a way."

"No, no," cried the girl. "How could you have foreseen such a thing?"

Marable shook his head. "Those eyes, you know. I should have taken precautions. But I had no idea it could burst from its prison so."

For the first time Marable had definitely mentioned his idea of what had occurred. The girl had understood it all along, from their broken conversation and from the look in the young scientist's eyes.

She sighed deeply. "You will get a revolver before you search further?"

she said. "I'm going to. Smythe has one, and I know he'll lend it to me."

"I will," he promised. "You know, Leffler has the same idea we have, I think. That's why he keeps talking about it being our fault. I believe he has seen something, too. His talk about the devil inside the block was half in earnest. I suppose he put it down to imagination, or perhaps he did not think this fossil to be dangerous."

They went out together, and walked toward the restaurant they frequented. Her father was there, lunching with one of the superintendents of the museum. He smiled and waved to Betty.

Everyone, of course, was discussing the killing of Rooney.

After an hour, during which the two young people spoke little, Marable and Betty Young left the restaurant and started back toward the museum.

Her father was still at his table.

They walked up the driveway entrance, and then Marable uttered an exclamation. "Something's wrong," he said.

There was a small crowd of people collected on the steps. The outer doors, instead of being open as usual, were closed and guards stood peering out.