"You happened to be available and more or less on the spot, and he said you had the sort of mind that might pick up the invisible factor. I asked him what he meant, and he said that at all closely guarded headquarters there's bound to be an invisible man—a man everyone takes so much for granted that he just isn't noticed—gardener, window cleaner, postman. I said that SHAPE had thought of that, and that all those sort of jobs were done by enlisted men. M told me not to be so literal-minded and hung up." Chap. 1, p. 13

"The invisible factor. The invisible man. The people who are so much part of the background that you don't know if they're there or not. Six men and two girls and they hardly spoke a word of French. Good cover, gipsies." Chap. 1, p. 21

"Not wanting to...