Casey began to stand, but the professor raised a hand. “Wait a moment,” he said. “I’d like to ask you a few questions.”

The Pacifist looked at the other warily.

LaVaux said, “You’re the first member of your organisation to whom I’ve ever spoken.”

“I doubt it,” Casey said.

“Ah? Very secret, eh? Members are everywhere, but undetected. Then how do you recruit new membership? Being as illegal as you are, of course, the initial approach must be delicate indeed.”

“That’s right,” Casey nodded. “We take every precaution. A prospect isn’t approached until it is obvious he is actually seeking an answer to the problem of outlawing war. Many persons, Professor, come to our point of view on their own. They begin discussing the subject, seeking answers, seeking fellows who think along the same line.”

The professor was fascinated. “But even then, of course, mistakes must be made and some of your membership unmasked to the authorities.”

“A hazard always faced by an underground.”

“And then,” the professor said triumphantly, “your whole organization crumbles. One betrays the next, under police coercion.”

Casey laughed sourly. “No. That’s not it. We profit by those who have gone before. The history of underground organizations is a long one. Professor. Each unit of five Pacifists know only those belonging to their own unit, and one co-ordinator. The co-ordinators, in turn, know only four other co-ordinators with whom they work, plus a section leader, who knows only four other section leaders with whom he works, and so forth right to the top officials of the organization.”

“I see,” the professor murmured. “So an ordinary member can at most betray four others, of course. But when the police capture a co-ordinator?”

“Then twenty-five persons are endangered,” Casey admitted. “And occasionally it happens. But we have ten of thousands of members, Professor, and new ones coming in daily. We grow slightly faster than they seem able to catch us.”