Medium-future post-disaster/alien-contact hybrid, from one of science-fiction's most durable veterans (Lifeburst, Manseed, etc.). Earth's technology and space colonies have been all but annihilated by the blundering offspring of a monstrous space-beast. A few people survive on Earth in barbaric conditions; a few more live in space habitats in the ""halo"" (Oort cometary cloud) courtesy of the ""eldren,"" a peaceful, nonviolent association of hundreds of alien races who have taken up residence there. The eldren, alas, refuse to admit savage humanity to the association, but young Benn hopes to prove his species worthy by playing the game of Blade and Stone, a set of planetary puzzles designed to test eldren young. Then the eldren computers and communicators come under attack and fall silent, while--coincidentally?--three hitherto unknown aliens show up--but only Benn's Hydran friend, Gibbon (whose clone-brother attempts to capture the aliens and is murdered), shows any concern. In the game of Blade and Stone, Benn is joined by two Earth survivors, Don Diego and Roxane, who've allied themselves with the alien newcomers in order to bargain with the eldren. Benn persuades Roxane that power games are not the eldren way--just before the Eldermost, a godlike being, emerges to deal with Don Diego and his evil allies, and mop up the invading computer-worm/creature that's attacking the computers and communicators. Solid, thoughtful, and well-handled, but YA-ish: should prove very popular with the younger sections of the audience.