Three nostalgic siblings (Lora, Leo, and Zac) return from the south of France to the alpine Italian village of Poggio Silente to spend their holidays with their grandfather, Tomás. What seems like a monotonous summer is transformed when they discover a Gothic labyrinth beneath the foundations of their stone house.
Without seeking it, they open an ancient, three-century-old mechanism. Leo and Zac, along with two local girls (Giulia and Alessia), turn out to be the rightful heirs to the bloodlines of the Order of the Acorn. One by one, the children are chosen by three lost relics: the Hat of the Rock, the Hat of the Earth, and the Hat of the Fauna. After joining forces to contain a rift of ash in the basement, they open the portal to the Eternal Glade, shattering three hundred years of absolute silence.
