A fistful of cultural conflicts centered on the ocean-covered planet Shora, where a thousand years have passed since the actions described in Slonczewski's hardcover debut novel, A Door Into Ocean (1986). Sharing Shora with the raft-dwelling, all-female, genetic-whiz Sharers are the floating cities of Elysium; the Elysians, immortal but sterile, are the leading bankers of the scattered human colonies of the Fold. Hearing disquieting reports of nuclear missiles on Urulan, a planet of warlike barbarians, the Elysians have invited translator Raincloud of the volcanic planet Bronze Sky to visit the Elysian city Helicon, to research Urulan goings-on; Raincloud's doctor husband, Blackbear, will help with Elysian research into reproduction and longevity. Numerous long-standing problems eventually threaten the status quo: a new supreme ruler emerges on Urulan, whence Raincloud must journey to defuse a threatening situation; various Heliconian secret banking projects become public knowledge, and the Sharers show their disapproval in traditional, nonviolent protests; the ubiquitous machines of Helicon, having become sentient and self-willed, make a bid for independence; meanwhile, a volcanic eruption on Bronze Sky wipes out most of Blackbear's family. A marvelous array of cultures presented in astonishing depth: an enormously impressive achievement, despite Slonczewski's inability to dramatize events rather than simply report them.