After Romilly's mother's death of a strange fever years ago, neighbours and family fled her village. Bereft, her father becomes increasingly withdrawn, revealing little of their family history that Romilly longs to understand. When her beloved uncle mysteriously disappears from his boat on a cloudless night at sea, she senses her father's growing terror a terror she shares when she spies an enormous Being opening a sail-shaped flap of sky over their wheatfield. Romilly suspects these inexplicable events are connected, but how? With the help of unlikely allies the healer Arra, Robbie the boisterous crow, and the kestrel Mira Romilly must convince her father to dismantle the wall to his greatest secret, and that of the Being that exists in the world beyond.