For thousands of years, the Earth has been enclosed by an impervious Shield raised by the long-vanished Ascended Ones. The world beneath consists of city built next to city, rising layer upon ancient layer. The planet itself, the configuration of the buildings, and the materials used in their construction generate ``plasm'' energy, which accumulates over time in odd nodes and nooks; the sole monetary standard, plasm may be stored or broadcast, and, tapped by a skilled human mind, can heal bodily injuries, enhance mental capacity, project astral bodies--can, indeed, accomplish true miracles--but a clumsy or overambitious operator risks immolation inside a gigantic fireball. Aiah, a lowly employee of the ubiquitous Plasm Authority, observes one such fireball, and infers the existence of a concentrated and hitherto unexploited plasm source completely outside Plasm Authority control. She decides to sell her source to the powerful Metropolitan, Constantine, and his gifted, ruthless assistant, Sonya, who trains Aiah in the ways of plasm use. Soon Aiah, rapidly becoming accustomed to the benefits of wealth and power, becomes Constantine's lover and, despite an initial reluctance, commits herself to helping him with his plans to attack and conquer a repressive rival city, thereby restoring the prestige forfeited by his family and people after their defeat in a previous power struggle. Williams (Aristoi, 1992, etc.) creates a curious, fascinating yet disconnected scenario--an effect heightened by a dearth of main characters (three, all above) and the present-tense narrative. The upshot is, by Williams's own high standards, unsatisfying.