Cosima Unfortunate has spent all her life at the Home for Unfortunate Girls – a school where any disabled children, or children deemed different, are sent, whether their families want it or not. It is there that she meets her friends – Pearl, Mary and Diya – and they start to practise mini heists involving the theft of cakes, biscuits and other sweet goodies.

But when Cos finds out that Lord Francis Fitzroy, the explorer behind the Empire Exhibition, is planning to adopt them, she and her friends plot the biggest heist of their life. Instead of fondant fancies, they’re going to steal Fitzroy’s prized tiara, containing the legendary Star Diamond of India! But, as they start preparing for the day, Cosima finds herself drawing ever closer to discovering the one secret she’s always wanted to know – the truth about her parents…