Everything in 12-year-old Pilar's world is changing. Her Chicago neighborhood is gentrifying and her chores have doubled since her sister, Lorena, left for college. The only constant is her family's code of silence around her cousin Natasha—who disappeared in the Dominican Republic fifty years ago during the Trujillo dictatorship.

When Pilar hears that there's a professor who studies disappearances under Trujillo, she hops on the next train downtown to the university. There, after snooping around the professor's empty office, she finds a folder with her cousin’s name on it . . . and literally falls into it.

Pilar lands on Zafa, an island alive with mythical warriors, demons, and a magical prison where Natasha is held captive. Pilar will have to go toe-to-toe with the Dominican boogeyman, El Cuco, if she has any hope of freeing Natasha and returning home.