Radical climate change that has reshaped human geography by the 24th century. Young Cree Indian geologist Keltyn SparrowHawk flies to Antarctica to scout for the strategic mineral iridium. After their plane crash-lands, Keltyn and her Canadian crew-mates discover the land is now home to the Onwei, a tribe of nomadic cattle-herders. She befriends two teens: orphan would-be gaucho Joaquin Beltran, and horsewoman Luz Hogarth, who is likewise searching for the elusive iris stone, from which her mother fashions fine jewelry. Despite scorn from tribal leaders and Keltyn's crew, she and Luz soon scramble up the slopes of the nearby Erebus volcano, scouting for iridium ore. Mortal danger awaits.
In its midst, Keltyn learns from her crew-mate, anthropologist Fay Del Campo, that their mission's sponsor, Sir Oscar Bailey, plans to use the metal to enable transport of Canadian colonists to Antarctica. Keltyn's loyalties are already in flux. Soon she plunges into an ill-conceived gamble that spirals into free-fall. A scheming bitter shaman and a vindictive new gaucho leader fan suspicion against the "Sky-Bornes." Luz and Joaquin are the only ones who can help, but each must first survive their own ordeals.
