

She is taken to the capital planet, Kharemough, and discovers that the Winters' prejudice against sibyls is a political tool used by the Hegemony to preserve its control of technology on Tiamat. On her way, she becomes entangled with smugglers and is taken off-world-a one-way trip for a Tiamatan citizen, as the Hegemony forbids Tiamat full access to their worlds. Moon receives a message, apparently from Sparks, urging her to come to Carbuncle, though the city is barred to sibyls.

Sparks, unable to join her among the sibyl mystics and curious about his offworld heritage, travels to Carbuncle, Tiamat's capital, where he is immediately caught up by Arienrhod and eventually becomes the "Starbuck": her consort and commander of the mer hunts. Sibyls enter a trance and by mysterious means, can answer questions. Moon becomes a sibyl, a position of high status among the Summer people, since they are keepers of knowledge freely available to anyone who asks. She and her cousin Sparks are lovers, and both are "merry-begots", conceived during the planetary festivals held every 20 years to remind Tiamat of the cycle of power. The novel follows Moon, the only one of these clones to survive to adolescence. She has secretly implanted several Summer women with embryos, clones of herself, in the hopes of extending her rule past her ritual execution at the end of Winter. This also allows a single Snow Queen to reign for the entire 150-year season, and it is with the Snow Queen, Arienrhod, that the story begins. Mers are hunted as frequently as possible during the Winter years, to the brink of extinction. The Hegemony's interest in Tiamat has to do with the "mers", sentient sea-dwelling creatures whose blood provides the "water of life", a virus that halts the aging process. Interstellar travel between Tiamat and the Hegemony is only possible during the 150 years of Winter rule, and a single woman rules the entire planet: a "Snow Queen" in Winter, a "Summer Queen" in Summer. Every 150 years, the suns orbit around a black hole dramatically impacts the planetary ecology and to keep the uneasy peace, the government switches from Winter rule to Summer rule under a matriarchal monarch. The residents of Tiamat are split into two clans: "Winters" who advocate technological progress and trade with offworlders, and "Summers" who depend on their folk traditions and rigid social distinctions to survive on this marginal planet.
