“But it was prehistoric.”

“Not exactly. It wasn’t a product of genetic declension. It was an animal that was thought to be extinct but had simply gone unchanged since prehistoric times.”

“Got it. Like cockroaches.”

“Exactly like cockroaches. Science comes across those once in a while, like the Blewitt’s owl that was thought extinct for over a century and was found a year ago in the woods of India, alive and well.”

“That’s too bad, about the fish. I thought I had something.”

“Evolution doesn’t work in reverse,” Joyce said. “Elephants don’t suddenly become woolly mammoths and cats don’t become saber-toothed tigers. Once an attribute is discarded, it stays discarded.”

“But didn’t someone find woolly mammoths frozen somewhere in Siberia?” Gentry asked. “Weren’t they perfectly preserved and didn’t people even eat the meat?”

Joyce smiled slightly. It was a warmer smile than before. “Did you also read that when you were a kid?”

“As a matter of fact, I did. I read a lot back then. Books, comics, baseball card backs, cereal boxes. My mother left home, my dad worked, and we had shitty TV reception.”

“You also said something like that back at Grand Central. About loving to learn things when you were a kid.”

“I did love to learn. That’s one reason I became a cop. To follow clues. Figure things out.”

“Well, the thing about the mammoths is that they were dead. Even so, the fossil record doesn’t show anything resembling a giant bat. Like cockroaches and the coelacanth, bats have been around for more than fifty million years in more or less the form that you see them now.”

Gentry was silent again. This left him where he started, and his mind went looking for sensible explanations.

“Genetic drift is a possibility,” Joyce said, thinking aloud.

“Which is?”

“New animals sometimes evolve when a species splits into two or more new forms. That sometimes happens due to geographical isolation. Genetic recombination is also a possibility.”

“Is that the same as recombinant DNA?” Gentry said.

“Yes,” Joyce said. “It’s genetic engineering performed by nature. Sometimes chromosomes inherited from the parents swap segments because of physical breakage.”

“Because of-?”

“Could be a number of things. Radiation. Chemicals. Internal mechanisms we don’t understand. That can set up all new hereditary patterns.”

“How long does genetic recombination usually take?”

“It can happen quickly or it can take years. Two parents under six feet tall can produce a child seven to eight feet tall. Or the height of humans can increase steadily over centuries. There are no rules.”

They reached Gentry’s apartment building. The front door was propped open with a wedge. One exterminator was spraying the hallway, another was in Mrs. Bundonis’s apartment. The scent was like mildew. Gentry walked in holding the large pizza. Joyce was right behind him holding her nose.

“How’s it look?” Gentry asked the woman spraying in the corridor.

“Like your usualcucaracha infestation,” the middle-aged woman said as she continued spraying.

“Usual?”

“Hit-and-hide. They’ve got legs designed for running and antennae that tell them where to run. Toward food, away from danger. They pour into a place and then they seem to disappear. But they haven’t. They’re hiding in every damn place you can think of. In drains and behind cabinets and under refrigerators or stoves or toilets. They’re also in some places you wouldn’t think of, like Mr. Coffee filter pots and inside computer printers.”

“Did you ever hear of a swarm this size?”

“I never see a swarm of any size. I usually get someplace after most of them are hiding.”

“Right,” Gentry said. “But have youheard of one? Why would they swarm in the thousands?”

“Roaches are funny. They find all kinds of reasons to move around. A change in temperature, a flood, a food shortage-”

“Predators?”

“Oh, yeah.”

“Bats?”

The exterminator shrugged. “Why not? I found some kinda foul dung down in the basement. Could’ve been guano.”

“Any idea how bats might have gotten in there?” Gentry asked.

“There’s a drain in the floor down there,” the exterminator told him. “Looks like it once emptied into the river, probably as part of an old sewage system. I found it when I saw cockroaches coming out from under an old desk and moved it. The metal drain cover was rusted. This close to the water, everything rusts. Your super’ll have to get that taken care of. Maybe bats or even seagulls found a nest of roaches near the river and started feeding on them. One nest spills into another, that one into another-pretty soon you have a stampede.”

Gentry thanked the woman. Then he and Joyce squeezed by her.

When they reached the apartment, Gentry handed Joyce the pizza and pulled his keys from his pocket. “This place was not exactly clean when I left.”

Gentry stepped into the short hallway and switched on the light. The first impression wasn’t as bad as he expected. Ahead, in the small living room, the blinds were up and the sunlight made things seem a little cleaner. And he’d thrown out the Thai food he’d been eating, so the cockroaches wouldn’t get it. To the right, the bedroom door was shut. The detective took the pizza back, then held it high so Joyce could enter. She walked in and he kicked the door shut with his foot. He watched her slender form as she moved ahead, framed by the bright window.

“Very sunny,” she said.

Joyce turned around in the living room and then faced him. He couldn’t see her expression, but he could feel her eyes. His breath came a little faster, and he felt a kind of longing that he hadn’t experienced in a very long time. He turned away-not to avoid the feeling but to freeze-frame it.

He walked into a small kitchenette to the left and put the pizza on a tiny drop-leaf table. “Where do you live?”

“Up in the Bronx.”

“Is it pretty safe where you are?”

“Very. I carry a thirty-eight when I go to work. Licensed and loaded.”

Gentry shot her an approving look. Not because she was a lady with a gun but because she was smart.

“You take it to a firing range, keep it in good shape?”

“Oh, yeah. I grew up with guns. The thirty-eight was a high school graduation present from my dad.”

“We’ll have to go shooting sometime.”

“That might be fun.”

Gentry went back to the pizza. He wasn’t thinking about bats just then. A lot of longings were coming back.

He pulled a cookie sheet from under the sink and aluminum foil from a cabinet. “How long have you been at the zoo?”

“Going on three years.”

“I bet there’s a lot of competition for jobs like that. Curators and heads of departments, that sort of thing.”

“It’s pretty intense.” Joyce’s voice had dropped a little and she did not elaborate. She ambled toward the computer, then turned back. “Is there anything I can do?”

“Actually, yes,” Gentry said. “Boot the computer. Just turn on the surge protector under the desk-everything else’ll come on.”

Joyce bent over the folding chair. The surge protector was lying on its side on the floor amid a cluster of dust bunnies. She switched it on. The computer and monitor snapped to life.

Joyce got onto the Internet and typed in two keywords:bat andanomalies. She sat back as Gentry put the pizza in the oven, then poured Cokes for them both.

The first list of ten articles and Web sites popped up after a few seconds. Joyce scanned the headings. The first article was about bats that had recently been lured from caves to farms in Colorado in the spring and so far ate nineteen million rootworms, saving a fortune in pesticides. There were also articles on the reproductive habits of the world’s smallest bats, on bats that lived more than twenty-five years, and on tiger moths that emitted high-frequency clicks that disoriented attacking bats and forced them to break off their attacks.