"Of course," Nedra answered.
"But why haven't Cal and his buddies found it?"
"They don't even know we exist," Nedra explained. "And if they did, for some reason they wouldn't like to come into the tunnels."
"In effect, the tunnel is wired," West said.
"Do you mean they would get a jolt of high voltage electricity if they ventured in here?"
"Nothing as crude as that," the craggy man replied. "However, at two places, high frequency generators are built into the walls and hidden in such a manner that a person entering the tunnel is saturated with their radiations, which trigger the adrenals in his body. The result of this is that he suddenly feels very much afraid."
"Eh?" Zen said, startled. "A fear generator?"
"In effect, it is that."
"But that would be a very powerful weapon."
"Yes, it would," the craggy man said, his voice dry.