Strange Highways

rose from a crouch. "I've already seen how they got out of the room itself. Have you?"
     "Yeah."
     They went to the far end of the long room. Near floor level, something had tampered with an eighteen-inch-square intake duct to the building's ventilation system. The grille had been held in place only by light tension clamps, and it had been torn away from the opening behind it.
     Acuff said, "Have you looked in the exchange chamber?"
     Because of the nature of the work done in lab number three, all air was chemically decontaminated before being vented to the outside. It was forced under pressure through multiple chemical baths in a five-tiered exchange chamber as big as a pickup truck.
     "They couldn't get through the exchange chamber alive," Acuff said hopefully. "Might be eight dead rats in those chemical baths."
     Ben shook his head. "There aren't. We checked. And we can't find vent grilles disturbed in other rooms, where they might have left the ducts-"
     "You don't think they're still in the ventilation system?"
     "No, they must've gotten out at some point, into the walls."
     "But how? PVC pipe is used for the ductwork, pressure sealed with a high-temperature bonding agent at all joints."
     Ben nodded. "We think they chewed up the adhesive at one of the joints, loosened two sections of pipe enough to squeeze out. We've found rat droppings in the crawl-space attic ... and a place where they gnawed through the subroof and the overlying shingles. Once on the roof, they could get off the building by gutters and downspouts."
     John Acuff's face had grown whiter than the salt part of his salt-and-pepper beard. "Listen, we've got to get them back tonight, no matter what. Tonight. "
     "We'll try."
     "Just trying isn't good enough. We've got to do it. Ben, there are three males and five females in that pack. And they're fertile. If we don't get them back, if they breed in the wild ... ultimately they'll drive ordinary rats into extinction, and we'll be faced with a menace unlike anything we've known. Think about it: smart rats that recognize and elude traps, quick to detect poison bait, virtually ineradicable. Already, the world loses a large portion of its food supply to rats, ten or fifteen percent in developed countries like ours, fifty percent in many third-world countries. Ben, we lose that much to dumb rats. What'll we lose to these? We might eventually see famine even in the United States - and in less advanced countries, there could be starvation beyond imagination."
     Frowning, Ben said, "You're overstating the danger."
     "Absolutely not! Rats are parasitical. They're competitors, and these will be competing far more vigorously and aggressively than any rats we've ever known."
     The lab seemed as cold as the winter night outside. "Just because they're a bit smarter than ordinary rats-"
     "More than a bit. Scores of times smarter."
     "But not as smart as we are, for heaven's sake."
     "Maybe half as smart as the average man," Acuff said.
     Ben blinked in surprise.
     "Maybe even smarter than that," Acuff said, fear evident in his lined face and eyes. "Combine that level of intellect with their natural cunning, size advantage-"
     "Size advantage? But we're much bigger
     Acuff shook his head. "Small can be better. Because they're smaller, they're faster than we are. And they can vanish through a chink in the wall, down a drainpipe. They're bigger than the average rat, about eighteen inches long instead of twelve, but they can move unseen through the shadows because they're still relatively small. And size isn't their only advantage, however. They can also see at night as well as in daylight."
     "Doc, you're starting to scare me.'
     "You better be scared half to death. Because these rats we've made, this new species we've engineered, is hostile to us."
     Finally Ben was forming an opinion of Project Blackberry. It wasn't favorable. Not sure he wanted to know the answer to his own question, he said, "What exactly do you mean by that?"
     Turning away from the wall vent, walking to the center of the room, planting both hands on the marble lab bench, leaning forward with his head hung down and his eyes closed, Acuff said, "We don't know why they're hostile. They just are. Is it some quirk of their genetics? Or