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Thirteen-year-old Dan Cahill and his older sister Amy are wanted by Interpol for a series of burglaries. But Amy and Dan are innocent of their crimes. A secret organisation known as the Vesperians has kidnapped seven members of the Cahill family. If Amy and Dan don't get the ransom, it will mean the death of all the hostages.

Till now, Amy and Dan have managed to stay one step ahead of the police and keep their family alive. But soon everything will change. Vesper One orders them to steal the Golden Jubilee, one of the world's largest diamonds. However, Amy and Dan don't know that it's really just a set-up... and someone will die anyway.