Indigo lives in the Lake District and spends his time exploring the mountains he loves. An unexpected parcel arrives containing a first aid kit inside his grandfather's satchel. Indigo's curiosity is raised as he looks through his grandfather's notebook to discover drawings of mythical creatures. Strange things begin to happen, and Indigo finds himself treating an injured magpie cat, curing a cockatrice of its death-darting gaze, and defending a dragon. Indigo realizes he must uncover the secrets his family have kept hidden and travels alone to the Polish mountains to search for his grandfather and the truth. Danger looms as events spiral out of control, and Indigo needs to make choices that change him, his world, and his future forever.