Book three in the acclaimed Edgar-and Agatha-Award nominated Oona Crate Mystery series. Thirteen-year-old magician/detective Oona Crate is gearing up for a series of highly difficult-and potentially lethal-magical battle tests. But when a break-in at the museum ends in the theft of a magical gem, Oona's attention is diverted as she attempts to discover who the thieves are before they can activate the gem's catastrophic powers.