Billy lingered a minute, listening, then decided to head back out to reassure the mother. He was almost there when he heard, from the hallway bathroom, a terrific BANG!—the sound of bottles falling into the bathtub—and a loud grunt and Vasiliy’s voice, grown fierce, spurting Russian invective.

The mother and daughter looked stricken. Billy held out a hand to them in a gesture of patience—having accidentally swallowed his gum—then rushed back down the hall.

Vasiliy opened the bathroom door. He was wearing Kevlar-sleeved trapping gloves and holding a large sack. Something in the sack was writhing and pawing. And that something was big.

Vasiliy nodded once and handed the sack to Billy.

Billy couldn’t do anything other than take it, otherwise the sack would fall and the rat would escape. He hoped the fabric was as sturdy as it seemed, the big rat twisting and fighting inside. Billy held the sack out as far from his body as his arm would reach while still allowing him to hold the flailing rat aloft. Vasiliy was, meanwhile, calmly—but too slowly—opening his cart. He removed a sealed package, a sponge prepared with halothane. Vasiliy took back the sack, and Billy was only too happy to relinquish it. He opened the top just long enough to drop the anesthetic inside, then closed it again. The rat struggled just as violently at first. Then it began to slow down. Vasiliy shook the sack to speed up the process.

He waited a few more moments after the fighting stopped, then opened the sack and reached inside, pulling the rat out tail first. It was sedated but not unconscious, its pink-digited front paws still digging their sharp nails into the air, its jaw snapping, its shiny black eyes open. This was a good-size one, maybe eight inches of body, the tail another eight. Its tough fur was dark gray on top, dirty white below. Nobody’s escaped pet, this was a wild city rat.

Billy had moved many steps back. He had seen plenty of rats in his day, yet he never got used to them. Vasiliy seemed to be okay with it.

“She’s pregnant,” he said. Rats gestate for just twenty-one days and can birth a litter of up to twenty pups. One healthy female can breed two hundred and fifty pups each year—with half of that litter more females ready to mate. “Want me to bleed her for the lab?”

Billy shook his head, showing almost as much disgust as though Vasiliy had asked if he wanted to eat it. “The girl had her shots at the hospital. Look at the size, Vaz. In the good name of Christ. I mean, this isn’t”—Billy lowered his voice—“this isn’t some tenement in Bushwick, you catch my drift?”