Ariadna discovers that her grandfather has long been searching for the remains of her father, who disappeared during the Spanish Civil War. Determined to assist him, she travels to Burgos, where a mass grave is being exhumed, and where her father could potentially be buried. During her stay there, she will learn the story of Antoni Benaiges, a young teacher from Tarragona who, before the war, was her grandfather's professor. Through an innovative pedagogical method, Antoni inspired his students and made them a promise: to take them to see the sea.