Two space-colony kids defeat alien invaders with the help of a super biocomputer. Teen-age Kate and her young friend William are children of research scientists investigating Plioctis, an alien world far from old Earth. Leaving the protection of ""the dome"" to search for a lost cat, Kate and William see the colony's chief scientist go to investigate an alien pyramid. Returning to the dome, they find it wrecked and empty. When the scientist arrives, dying from exposure to a mysterious power in the pyramid, he tells a horrifying tale of insect-like aliens who have savaged the dome and kidnapped the inhabitants. Their radio suddenly comes to life to tell them that these creatures are the Dissgatts, ancient enemies of mankind, but that Ashar of Qarius is coming to help them. On arrival, Ashar appears to be a supercomputer--but he's really an artificial being made by the Dissgatts: an Egyptian boy grafted onto a Dissgatt body. With his help, the aliens are subdued and the colony reunited. Too much here fails to hang together, or doesn't make sense. Why Egypt? Why does Ashar destroy the Dissgatts? Why drag in the supposed inability of children bred for intelligence to be compassionate? why the subplot about a venial space captain? Something of a mishmash, though this may be useful in collections with voracious scifi readers.