The orbiting research station of Delta III has received three major additions to the fledgling study of sentient alien organisms: ""snowballs"" from a world of violent temperature extremes, ""dragonfish"" from a planet covered with water, and a pair of wind-riding ""mantas"" from a fierce desert environment. A malfunctioning life-support system exposes a researcher to the atmosphere of the mantas' cage; at once a deadly plague, with bewildering psychological manifestations apparently triggered by the alien animals, begins to spread through the ship. By the time Rob McGreggor, a parasitologist with a special knowledge of ""vectors"" (pathogen-transmitting organisms), isolates the factors necessary to produce antibodies against the disease, only a fearfully long shot can save the remaining crew. The idea is so promising that one hates to report that Jack Haldeman (brother of the more accomplished Joe) hasn't done very much with it. In fact, this is more like an early draft for a novel--fair writing, but an uncoordinated narrative--than the real thing.