This magical realism novel begins in 1970, with Esmeralda Luna, a recent graduate of the University of Oregon, suddenly learns that her widowed father has been reported missing, and is believe to be somewhere in Mexico. Despite her godparents’ warnings, Es ventures down to the volcano-ridden area of the Pico de Orizaba. Relying on cryptic clues as to her father’s whereabouts, Es and her adopted dog, Xolo hike into the hidden valley of Citlatépetl where she confronts an ancient Aztec curse. The quest reveals many masked secrets of her father’s early efforts to save the environment and her mother’s vow. Es delves into a world of magic, half-human creatures, and the unending battle between good and evil.