Gullstruck IslandFrances Hardinge2008

On Gullstruck Island the volcanoes quarrel, the jungles sing and occasionally a Lost is born - a child seemingly a halfwit but with the power to depart its body and mind-fly with the winds. Hathin and her sister Arilou are members of the Lace - a tribe ostracized for terrible ancient crimes. However, Arilou is also a Lost, the clan's most precious commodity. The other islanders will give anything to see what she sees. But Hathin and her people have a secret - in truth, Arilou's mumblings make no sense. Only Hathin's trickery keeps the pretence alive. So when the lie that has protected Hathin's village for so long threatens to turn against them, what else can Hathin do but take her halfwitted sister and run?