Brooklyn teenager Sierra Santiago is an artist, painting her first full-size mural on an abandoned building under the approving eye of her grandfather's domino-playing friends. But something's happening to the murals in her neighborhood: One by one they're fading too quickly, some of the faces in them shifting from joy to terror, some of them shedding tears. Sierra thinks she must be imagining it — until her grandfather, bed-ridden after a stroke, gains enough lucidity to try to tell her about the sorcerors, called shadowshapers, in her lineage, and the danger threatening them. It's crucial, he says, that she finish the mural as quickly as possible.