Pendergast retrieved his briefcase, snapped it open, and withdrew a fat computer printout. “I have a report on DNA from the claw found in one of the first victims. Of course, I can’t show it to you. It would be highly irregular. The New York office wouldn’t like it.”
“I see,” said Frock. “And you continue to believe that the claw is your best clue.”
“It’s our only clue of importance, Dr. Frock. Let me explain my conclusions. I believe we have a madman loose in the Museum. He kills his victims in a ritualistic fashion, removes the back of the skull, and extracts the hypothalamus from the brain.”
“For what purpose?” asked Frock.
Prendergast hesitated. “We believe he eats it.”
Margo gasped.
“The killer may be hiding in the Museum’s subbasement,” Pendergast continued. “There are many indications that he has returned there after killing, but so far we’ve been unable to isolate a specific location or retrieve any evidence. Two dogs were killed during searches. As you probably know, it’s a perfect warren of tunnels, galleries, and passages spread over several subterranean levels, the oldest dating back almost 150 years. The Museum has been able to furnish me with maps covering only a small percentage of its total area. I call the killer ‘he’ because the force used in the killings indicates a male, and a strong one at that. Almost preternaturally strong. As you know, he uses some kind of three-clawed weapon to disembowel his victims, who are apparently chosen at random. We have no motive. Our interviews with selected Museum staff have turned up no leads as yet.” He looked at Frock. “You see, Doctor, our best clue remains our only clue—the weapon, the claw. That is why I continue to search for its origin.”
Frock nodded slowly. “You mentioned DNA?”
Pendergast waved the computer printout. “The lab results have been inconclusive, to say the least.” He paused. “I can see no reason not to tell you that the test on the claw turned up DNA from various species of gecko, in addition to human chromosomes. Hence our assumption that the sample might be degraded.”
“Gecko, you say?” Frock murmured in mild surprise. “And it eats the hypothalamus ... how extraordinary. Tell me, how do you know?”
“We found traces of saliva and teeth marks.”
“Human teeth marks?”
“No one knows.”
“And the saliva?”
“Indeterminate.”
Frock’s head sank down on his chest. After a few minutes, he looked up.
“You continue to call the claw a weapon,” he said. “I assume, then, that you continue to believe the killer is human?”
Pendergast closed his briefcase. “I simply don’t see any other possibility. Do you think, Dr. Frock, an animal could decapitate a body with surgical precision, punch a hole in the skull and locate an internal organ the size of a walnut that only someone trained in human anatomy could recognize? And the killer’s ability to elude our searches of the subbasement has been impressive.”
Frock’s head had sunk on his chest again. As the seconds ticked off into minutes, Pendergast remained motionless, watching.
Frock suddenly raised his head. “Mr. Pendergast,” he said, his voice booming. Margo jumped. “I’ve heard your theory. Would you care to hear mine?”
Pendergast nodded. “Of course.”
“Very well,” Frock replied. “Are you familiar with the Transvaal Shales?”
“I don’t believe so,” said Pendergast.
“The Transvaal Shales were discovered in 1945 by Alistair Van Vrouwenhoek, a paleontologist with South Africa’s Witwatersrand University. They were Cambrian, about six hundred million years old. And they were full of bizarre life forms the likes of which had never been seen before or since. Asymmetrical life forms, not showing even the bilateral symmetry of virtually all animal life on earth today. They occurred, coincidentally, at the time of the Cambrian mass extinction. Now most people, Mr. Pendergast, believe the Transvaal Shales represent a dead end of evolution: life experimenting with every conceivable form before settling down to the bilaterally symmetric form you see today.”
“But you do not hold such a view,” Pendergast said.
Frock cleared his throat. “Correct. A certain type of organism predominates in these shales. It had powerful fins and long suction pads and oversized crushing and tearing mouth parts. Those mouth parts could saw through rock, and the fins allowed it to move at twenty miles per hour through the water. No doubt it was a highly successful and quite savage predator. It was, I believe, too successful: it hunted its prey into extinction and then quickly became extinct itself. It thus caused the minor mass extinction at the end of the Cambrian era. It, not natural selection, killed off all the other forms of life in the Transvaal Shales.”