But…

There was always a but. While Joyce felt at home with the unknown, she hated not knowing things. And the past fifteen or so hours had severely tested her patience. When she was a graduate student at New York University, doing fieldwork with Professor Lowery-who also became her first lover, deep in a bat cave in the Pyrenees-the older man worried about her low threshold for frustration. He advised his pupil to look at puzzles with a relaxed mind, to view them as an opportunity to add something to the annals of science. Unfortunately, Joyce just couldn’t think like that.

“You doing okay?” Gentry asked.

His voice startled her. For a moment, Joyce felt as if she’d been alone. “I’m fine. Why?”

“Just making sure. A lot of things can get to you down here. Sore feet. Thirst. Nerves.”

“No, I’m good.”

Gentry put his hands on her shoulders and moved around her. He sidled up to Arvids. “How well does your radio work down here?”

“Depends on how far down you go or how many walls get between you and the operator. So far I’ve never had a problem. Why?”

“Just curious. We’ve had trouble with our radios with all the new construction in midtown. The layers of electronics going into offices and residential buildings are acting like walls. Say,” Gentry turned to Joyce, “you said on TV that bats aren’t bothered by microwaves.”

“That’s right.”

“What about electronic noise? Could a city full of it draw them to a place or disorient them?”

“Draw them, no. Most bats ignore any sound beyond an average radius of fifty yards. And within that radius they pay attention only to sounds made by fellow bats or potential prey or predators.”

“Do they listen the same way humans do,” Gentry asked, “or do they use those echos?”

“Mechanically, bat hearing is the same as human hearing, albeit much more sensitive. When they echolocate, they ignore other sounds, pretty much the way people do when they’re talking in a subway or at a bar. The rest of the time bats listen the way other animals do.”

Arvids asked, “If there are still any bats down here, will they hear us coming?”

“They can hear an insect walking on sand six feet away.”

“I guess that would make us sound like a brass band.”

“Fife and drum corps would be more accurate,” Joyce said. “If there are bats within a mile of here, they heard our breathing and heartbeats about the time we entered the tunnel. To answer your other question, Detec-Robert,” Joyce went on, “electronics can disorient bats. Certain kinds of tiger moth emit high-frequency clicks that turn the normal flow of echo information into gibberish. We’ve been able to duplicate those signals in a lab.”

“Stealth moths,” Arvids said. “Nature is amazing.”

“Totally,” Joyce agreed. “Electronics can also confuse bats, but only if they happen to replicate a known sound-for example, a baby bat calling to its mother or a female to a male. And once the bat got a look or whiff of the computer or fax machine or whatever it happened to be, and saw that it wasn’t a fellow bat or prey, it would break off at once.”

“Pretty clever creatures.”

“They’re one of a kind,” she said proudly. “Did you ever hear of Operation X-Ray?”

Gentry said he hadn’t.

“During the Second World War, the Allies came up with a plan to drop thousands of bats from high-altitude bombers over Japanese cities. Each bat was going to be equipped with a large wax capsule strapped to its back. As the bats flew down, their body temperature would slowly melt the wax. Inside the capsule was a highly flammable liquid that would ignite when exposed to air. The bats were trained to fly toward certain sounds-air raid sirens, railroad whistles, maritime bells. They were also conditioned to fly toward searchlights. The idea was that they’d roost in strategic buildings in Japanese cities, self-immolate, and burn the buildings to the ground.”

“You’re kidding.”

“No. And there was no way to stop the bats. At night, even the best sharpshooters would have had an impossible time trying to gun them down. And even then there was always the risk that a bullet would penetrate the wax, set the bat on fire, and accomplish the mission.”

Gentry said, “I can just imagine what you think of the plan.”

“Why? Because bats were dying?”

“Well, yes.”

Joyce shook her head. “I’m not an animal rights activist. I hate cats, I enjoy hunting and eating deer and boar, and I’m all for using mice as medical test subjects.I lost a father to brain cancer and a grandfather to pancreatic cancer. I’d rather lose mice.”

“Hear, hear,” Arvids said.

“Besides, the bats were bred especially for Operation X-Ray. I think the plan was inspired. By targeting specific buildings the military could save human lives on the ground and in the air.”

“So what happened?” Gentry asked.

“During test runs in the desert, several dozen bats proved to be smarter than the scientists who’d conditioned them. They flew off and returned to where they were trained-bats have an incredible homing sense-and burned down the barracks.”

“Stealth moths and commando bats,” Arvids said. “Man, even zoologists see more action than I do.”

It took nearly half an hour of moving slowly through the darkness before they came to where the maintenance worker had fainted. The mound of guano was lying beneath a girder, between two sets of tracks. Joyce took the flashlight from Arvids. She circled the mound slowly. Arvids put his hand in front of his mouth. Gentry winced.

“I’ve never seen anything like this,” Joyce said.

“Jesus,” Gentry said. “The size alone probably put the maintenance man out, once he realized what it was.”

“The size is incredible, but so is the singular consistency,” Joyce said. “This is not a typical bat mound. This is like something you’d find in the elephant cage at the zoo.”

“That’d be a new one for the Transit Authority,” Arvids said from behind his splayed fingers. “An elephant infestation.”

“No, this was definitely left here by bats.” Joyce moved in closer. “The smell alone tells you that. The point is, when bats cluster in a small area like this, the guano falls in different ways, at different times. You can usually see the separate segments, different color and texture.”

“Like horse apples,” Gentry said.

“Exactly.”

“Excuse me, but this is more than I wanted to know,” Arvids said. He turned away.

Joyce shined the flashlight almost directly overhead. There were two horizontal concrete columns built perpendicular to the track. A naked metal girder, rusted from seeping water, was stuck between them. There were traces of guano from one side of the girder to the other. “What I don’t understand is why the bats would have come here, done this, and then left.”

“Like you said before,” Gentry pointed out, “this could be a migration rest area.”

“No. In that case the guano would have been spread across the tunnel, not centralized here.”

“Then how many bats do you think did this?” Gentry asked.

“I don’t know that either.” The scientist turned the flashlight back on the mound and walked around the base. “There’s a lot of spread at the bottom of the pile. See that?” She shined the flashlight on a wide, murky pool of liquid surrounding the mound.

“New York’s an extremely leaky island. River water and rain are constantly seeping in and dissolving soft biodegradable matter. Groundwater like that along with vibration from passing trains caused the waste to settle. And the weight of the mound caused the fluid content to sink and separate, compacting the mass above. So it’s impossible to say how many animals contributed to this or when it was started. It could have been a hundred bats over a few days or several thousand bats over a few hours.”

“Severalthousand bats?” Gentry asked. “There could really be that many bats down here?”