The Devil and His Boy by Anthony Horowitz
Chase through the streets of Elizabethan London in this historical adventure from the creator of Alex Rider. London is dirty, distant and dangerous ... but that's where orphan Tom Falconer is heading. And he's got a whole assortment of vicious criminals hot on his heels. Tom is helpless and alone until he meets Moll Cutpurse, a thirteen-year-old pickpocket. Together they find themselves chased across the city by the murderous Ratsey. But it's only on the first night of a new play - The Devil and his Boy - that Tom realizes that the fate of the Queen and indeed the entire country rests in his hands.