It is 1970 and Esmeralda Luna, a recent University of Oregon graduate, suddenly learns that her widowed father has been reported missing and is believed to be in Mexico. Despite her godparents' warnings, Es boldly travels to the volcano-ridden area of the Pico de Orizaba where her father is assumed to have ventured. Relying on a cryptic clue as to his whereabouts, Es and her adopted dog Xolo, hike not the hidden valley of Citlatépetl where she confronts an ancient Aztec curse that threatens of impede her quest. The journey reveals many masked secrets about her father's early efforts to save the environment and her mother's mysterious vow, that plummet Esmeralda into a world of magic, half-human creatures, and the unending battle between good and evil.