Astrid has lived in the rhubarb shed her whole life. The outside world is dangerous, Mama explains; she will understand when she’s older, but she cannot set foot beyond the door. Astrid longs to see the world; to meet other children; to live in the farmhouse with Mama.

But what she longs for most of all is to see the stars. Then one night, a stranger unlocks the shed: a stranger with wings. She has come to take Astrid to a secret city in the sky called London Overhead, far above the highest peak of the Shard.

For Astrid, like her, is a Librae – and will soon grow wings of her own . . .

Astrid is swept into a breathtaking and magical world of new friendships, sweeping adventures and unimaginable discoveries at the ancient, beautiful school for Librae students: Starminster. But quickly she learns that all is not well in the glimmering city. And when rumours abound of missing children in London Underfoot, she begins to realise that Mama may have been right about the dangers waiting for Astrid all along .