Men battle machines on a hostile alien planet, with the survival of the human species at stake: an old-hat outline that leading scientist/writer Benford invests with new and vibrant life. The humans of planet Snowglade, descendants of an exploratory expedition, have been driven forth from their Citadels and now exist only as scattered, harassed bands constantly threatened with extinction. Their enemies are the ""mechs,"" members of an advanced, intelligent, mental-organic machine civilization. The humans survive by raiding mech factories and stores; in retaliation, the mechs have evolved specialized humanhunter/killers like the Mantis, which can project complex illusions and--horribly--absorb the minds and personalities of its unfortunate victims. When Family Bishop loses its old, wise Cap'n, Fanny, to the Mantis, the survivors--including Killeen and his son Toby--encounter another Family led by Hatchet. With the cooperation of a renegade mech, Hatchet has set about building a new Citadel and urges Killeen's bishops to join in. But soon Killeen learns that the Mantis has been controlling Hatchet and protecting his primitive Citadel; the Mantis, you see, is curious about human psychology and creates grotesque, replusive ""art forms"" from the personalities it absorbs. Aided by a mysterious messenger from space (powerful enough to daunt even the Mantis), Killeen learns the whereabouts of an ancient buried spaceship and, along with a handful of like-minded freedom-fighters, departs in it. The Mantis, able to select more experimental victims from the humans who prefer to stay in the new Citadel, is content to let them go. Gripping, stirring, sometimes horrifying work, packed with glowing detail and astounding extrapolation--though not even Benford's considerable talents can wholly conceal the disappointing triteness of the plot.