Sierra Santiago looks forward to a summer of working on the mural she is painting in her Brooklyn neighborhood. While working on her dragon mural, she notices other murals in the neighborhood are changing.  Her abuelo, Lazaro, is acting even more strangely after suffering a stroke.  He keeps mumbling to Sierra that he is sorry.  Then Lazaro speaks clearly to warn her she must finish her mural. “They are coming for us!” he warns.  Sierra meets Robbie, another young artist in the community, at a party. She confides in him about the changes she is noticing in the neighborhood, Robbie starts to explain the ancestral ways of their culture, but they are interrupted by a creepy being that they just barely escape.  Sierra discovers the secrets of her ancestors, and she must use them to protect her family and her neighborhood.