By about 2170, the Endless City occupies the entire coast of North Africa; its Borderers live in poverty and squalor under a perpetual cloud generated by global warming and climate control. Though Father John Alston (``Fatoo''), of the Pandera presbytery, has lost much of his faith, he continues to offer the Borderers spiritual comfort and such medical aid as much as he is able (his own implants keep him safe from Borderer ailments, but the reverse isn't true). The Borderers chew a leaf, koiyl, similar to coca, that John suspects may cause cancer. Helped by Laurie Kalmar, a European-educated Borderer computer-net expert, he finds that the leaf from one particular source is dangerously radioactive. After he and Laurie become lovers, John visits home--where his once- genius brother, Hal, having monkeyed with his implants, has lain in a deathly coma for 20 years--and decides to leave the priesthood. Upon his return to the Endless City, his relationship with Laurie collapses; he tracks down the distribution of the deadly koiyl, which he begins to use himself, falls ill, returns home, recovers, allows Hal to die and, recognizing that his life is a spiritual journey, recovers his faith. Despite the highly unlikely extrapolation from now to then, especially the improbably secular North Africans: a thoughtful, sometimes wrenching, noteworthy debut.