Was he alone? Troy thought so. He couldn't make out the words, but it was a monologue, not a conversation. He had the impression of Clingman dictating another rambling dissertation on Tareeg ways into a recorder; and the conviction came to him, not for the first time, that the man was in some essential manner no longer sane, that he had come to believe that his observations on these deadly enemies some day really could be compiled into an orderly and valuable addition to human knowledge. Sane or not, he was a frightened man, the perfect quarry for Troy's present purpose. With a gun on him, he would talk. And once having assisted Troy to any degree, he would be too terrified of Tareeg reprisals to do anything but switch sides again and go along with Troy, hoping that thereby the worst--once more--could be avoided. The worst for Victor Clingman. It would be impossible, Troy thought, to trust Clingman, but he could make very good use of him in spite of that. He came quietly along the passage, his attention as much on the closed doors about him as on the one which was open. The guard's gun unfortunately wasn't a noiseless type, but he had wrapped a small cushion around its muzzle and across it, which should muffle reports satisfactorily if it came to that. Words became distinguishable. "It is not a parasite in the ordinary sense," Clingman's tired voice said. "It is a weapon. It kills and moves on. A biological weapon limited to attack one species: the enemy. It is insidious. There is no warning and no defense. Unconsciousness and death occur painlessly within an hour after contact, and the victim has not realized he is being destroyed. The radius of infection moves out indetectably and with incredible swiftness. And yet there was a method of containing this agent. That knowledge, however, is now lost. "As an achievement of the Tareeg genius for warfare, the weapon seems matched--in some respects surpassed--only by the one used to counteract it. And in that, obviously, there were serious faults. They...." The man, Troy decided, was quite close, perhaps twelve feet to the right side of the door. He glanced back along the silent hall, slipped the cover from the gun--with Clingman, he would only need to show it--then came into the room in two quick strides, turning to the right and drawing the door shut behind him. * * * * * There was no one in sight. The voice continued: