Che's family just moved to NYC from Bangkok. He's a long way from his home in Sydney, Australia, and his friends, and his boxing trainer. And the hardest part of being so far from home is keeping his ten-year-old sister under control. Rosa isn't like other kids. She's a troublemaker, but not in the ways you'd expect. Rosa is manipulative, and she shows no remorse. Che is pretty sure she's an undiagnosed psychopath--but he can't seem to get his parents to listen, and Rosa's behavior is escalating. 
 Engrossing, and a little creepy--that a child could mastermind the kinds of things Rosa does, and charm so many. (I mean, that's what psychopathy is, which is what makes it so terrifying.) The ending brings things together in a satisfying conclusion.