Moffett's sequel to the Ragged World (1991): a near-future saga of furry alien overlords demanding ecological retrenchment; judging by the evidence here, she's dug in for a long series, since none of the outstanding issues are settled or even given much of a workout. Instead, the story focuses on the alien Hefn's Bureau of Temporal Physics, set up to teach a handful of human mathematical whizzes how to use time-gates (by peering into the past, the Hefn hope to discover where humans fell off the ecological tracks) and, in particular, on two teenagers, Liam O'Hara and Para Pruitt, both misfits, both repressing sexual awareness, and both very fond of Humphrey, the Hefn in charge of the project. During a vacation, Liam and Para visit the Hollow, a famous homestead by the Kentucky river that Para has known and loved since childhood. The Hollow's present guardian, Jesse, is bitten by a snake and hospitalized, leaving Para and Liam in charge; Liam invites Humphrey to join them. But, nearby, a rabble-rousing, anti-Hefn preacher is stirring up the locals, already bitterly resentful of the Hefn's bans on high technology and human reproduction. Eventually, the preacher and his henchmen attack, intending to skin Humphrey alive, but a tornado (by coincidence?) kills them and helps convert the preacher into a Hefn advocate. Ecologically correct, with lots of well-handled teenage angst and convincing down-home detail; but--though the foreground is fine--the background remains nebulous, and readers curious about the Big Picture will find little but frustration here.