"Good, Dr. Leavitt. Saw you come in."

Leavitt introduced Hall to the security man, who then demonstrated the equipment to Hall. There were, the man explained, two radar scanners located in the hills overlooking the installation; they were well concealed but quite effective. Then closer in, impedance sensors were buried in the ground; they signaled the approach of any animal life weighing more than one hundred pounds. The sensors ringed the base.

"We've never missed anything yet," the man said. "And if we do . . . " He shrugged. To Leavitt: "Going to show him the dogs?"

"Yes," Leavitt said.

They walked through into an adjoining room. There were nine large cages there, and the room smelled strongly of animals. Hall found himself looking at nine of the largest German shepherds he had ever seen.

They barked at him as he entered, but there was no sound in the room. He watched in astonishment as they opened their mouths and threw their heads forward in a barking motion.

No sound.

"These are Army-trained sentry dogs," the security man said. "Bred for viciousness. You wear leather clothes and heavy gloves when you walk them. They've undergone laryngectomies, which is why you can't hear them. Silent and vicious."

Hall said, "Have you ever, uh, used them?"

"No," the security man said. "Fortunately not."

They were in a small room with lockers. Hall found one with his name on it.

"We change in here," Leavitt said. He nodded to a stack of pink uniforms in one corner. "Put those on, after you have removed everything you are wearing."

Hall changed quickly. The uniforms were loose-fitting one-piece suits that zipped up the side. When they had changed they proceeded down a passageway.

Suddenly an alarm sounded and a gate in front of them slid closed abruptly. Overhead, a white light began to flash. Hall was confused, and it was only much later that he remembered Leavitt looked away from the flashing light.

"Something's wrong," Leavitt said. "Did you remove everything?"

"Yes," Hall said.

"Rings, watch, everything?"

Hall looked at his hands. He still had his watch on.

"Go back," Leavitt said. "Put it in your locker."

Hall did. When he came back, they started down the corridor a second time. The gate remained open, and there was no alarm.

"Automatic as well?" Hall said.

"Yes," Leavitt said. "It picks up any foreign object. When we installed it, we were worried because we knew it would pick up glass eyes, cardiac pacemakers, false teeth—anything at all. But fortunately nobody on the project has these things."

"Fillings?"

"It is programmed to ignore fillings."

"How does it work?"

"Some kind of capacitance phenomenon. I don't really understand it," Leavitt said.

They passed a sign that said:

YOU ARE NOW ENTERING LEVEL I

PROCEED DIRECTLY TO IMMUNIZATION CONTROL

Hall noticed that all the walls were red. He mentioned this to Leavitt.

"Yes," Leavitt said. "All levels are painted a different color. Level I is red; II, yellow; III, white; IV, green; and V, blue."