From the author of Northshore, Southshore, and The Gate to Women's Country: an alien contact/planetary odyssey that just trundles along without provoking much reaction. A plague is ravaging the religion-dominated human empire--except for planet Grass, where the vegetation consists exclusively of. . .you guessed it. So the authorities decide to send a clandestine investigator, Marjorie Westriding Yrarier, and her family. After a long, difficult, and personally costly investigation, Marjorie determines the facts. Grass, it emerges, is home to an alien species that has two phases: the vicious, animal-like Hippae; and the gentle, civilized ""foxen."" The original human colonists used the Hippae as riding beasts and became enslaved by them. Previously, the Hippae had defeated another alien race of would-be colonists, and thus hoped to defeat galactic humanity by sending forth the same disease that devastated the aliens (thanks to a biochemical oddity, the humans of Grass are immune). Only when the activities of the Hippae provoke the humans to open warfare is the alien plot revealed. Imaginative and well worked out, but overstuffed, poorly peopled, and too long by half.