In a future Manhattan devastated by environmental catastrophes and epidemics, sixteen-year-old Lucy survives alone until vicious hounds target her and force her to join Aidan and his band. But soon they learn that she is the target of Sweepers, who kidnap and infect people with plague.

Fifteen-year-olds Mack, a high school drop-out but a genius with dogs, and Céce, who hopes to use her intelligence to avoid a life like her mother's, meet and fall in love at the restaurant where they both work, but when Mack lands in prison he pushes Céce away and only a one-eared pit-bull can keep them together.