Madeleine Tully lives in Cambridge, England, the World - a city of spires, Isaac Newton and Auntie’s Tea Shop. Elliot Baranski lives in Bonfire, the Farms, the Kingdom of Cello - where seasons roam, the Butterfly Child sleeps in a glass jar, and bells warn of attacks from dangerous Colours. They are worlds apart - until a crack opens up between them; a corner of white - the slim seam of a letter. Elliot begins to write to Madeleine, the Girl-in-the-World - a most dangerous thing to do for suspected cracks must be reported and closed. But Elliot’s father has disappeared and Madeleine’s mother is sick. Can a stranger from another world help to unravel the mysteries in your own? Can Madeleine and Elliot find the missing pieces of themselves before it is too late?

A mesmerising story of two worlds; the cracks between them, the science that binds them and the colours that infuse them.