Fermion Quirk's twin brother, Boson, is dead. These last few months he'd spent most of his time with the birds; he said they were angels and brought him his visions. Most of Carrick says the boy was a monster, but a few say he was a saint-in-the-making. The townspeople all look at Fermion now, and wait and wonder if she will go mad like her brother. Pa will talk about anything but Boson, and Moo's stopped talking entirely. Soon a voice starts rising in Fermion, telling her that she's the only one who can save her family. The voice says the cure lies on the other island, far out in the sea. But the Quirks have always been bog-folk: they don t go to sea. And even if Fermion manages to get to the other island, then what will she find?