to have no specific source, as if it were coming from every direction at once; and a numbing conviction arose in Halder that their minds were being destroyed in this room, that a methodical dissecting process had begun which would continue move by move and hour by hour until the Federation's scientists were satisfied that no further scraps of information could be drained from the prisoners. The investigation might be completely impersonal; but the fact that they were being ignored here as sentient beings, were not permitted to argue their case or offer an explanation, seemed more chilling than deliberate brutality. And yet, Halder told himself, he couldn't really blame anyone for the situation they were in. The Kalechi group represented an urgent and terrible threat. The Federation could not afford to make any mistakes in dealing with it.

"This image," the voice was saying, "represents a Great Satog, the oxygen-breathing, water-dwelling native of the world of Kalechi. There are numerous type-variations of the species. Shown here is the dominant form. It is highly intelligent; approximately a third of a Satog's body space is occupied by its brain.

"Kalechi's civilization is based on an understanding of biological processes and the means of their manipulation which is well in advance of our own. This specialized interest appears to have developed from the Satogs' genetic instability, a factor which they have learned to control and to use to their advantage. At present, they have established themselves on at least a dozen other worlds, existing on each in a modified form which is completely adapted to the new environment.

"Our occasional contacts with Kalechi and its colonies during the past two centuries have been superficially friendly, but it appears now that the Great Satogs have regarded our technological and numerical superiority with alarm and have cast about for a method to destroy the Federation without risk to themselves. A weapon was on hand—their great skill and experience in altering genetic patterns in established life forms to produce desired changes. They devised the plan of distributing Kalechi agents secretly throughout the Federation. These were to develop and store specific strains of primitive organisms which, at an indicated later date, would sweep our major worlds simultaneously with an unparalleled storm of plagues.

"The most audacious part of the Kalechi scheme follows. Ninety-two years ago, a Federation survey ship disappeared in that sector of the galaxy. Aboard it was a man named Ohl Cantrall, an outstanding scientist of the period. We know now that this ship was captured by the Great Satogs, and that Cantrall, his staff, and his crew, were subjected to extensive experimentation by them, and eventually were killed.

"The experimentation had been designed to provide Kalechi's master-biologists with models towards which to work. They proposed to utilize the high mutability of their species to develop a Satog type that would be the exact physical counterpart of a human being and could live undetected on our worlds for the several years required to prepare for the attack. They were amazingly successful. Each group of cells in the long series which began moving towards an approximation of the human pattern was developed only far enough to initiate the greatest favorable shift possible at that point in its genetic structure. Cell generations may have followed each other within hours in this manner, for over six decades.

"The goal of the experiment, the last generation issued in Kalechi's laboratories, were Satog copies of embryonic human beings. This stage was comprised of approximately twelve hundred individuals who were now permitted to mature and were schooled individually in complete isolation by Satog teachers. They were indoctrinated with their purpose in life ... the destruction of our populations ... and trained fully in the manner of accomplishing it.

"Eventually, each was shipped to a Federation world. Cover identities as obscure Federation