From the author of such incisive psychological thrillers as Roscoe's Leap (1987) and A Map of Nowhere (1989), an unassuming story for younger readers, with more depth than is at first apparent. David and Ben are unusually close, even for twins. When their plot to get even with the Wellington Street gang by prematurely lighting their Guy Fawkes bonfire goes awry, it also results in a magical manifestation of their unity: suddenly, Ben has the power to transform David's right arm into any object--a string of sausages, a snake to frighten the gang, even a plea for help after the gang retaliates by kidnapping Ben. Typically for Cross, what begins as a bizarre trick becomes the basis for thought-provoking action: unintended wounds and misunderstandings escalate the kids' feud until both twins begin to sympathize with their antagonists--and manage to achieve a reconciliation in which the magic arm plays an entertaining role. Though characterization here is minimal and the effort slight compared to Cross's YA novels, the action is lively and often funny. Better than average of its kind.