In May 1980, fifteen-year-old Oscar Drai suddenly vanishes from his boarding school. For seven days and nights no one knows his whereabouts . . .
His story begins in the heart of old Barcelona, when he meets Marina and her father, Ferman Blau, a portrait painter. Marina takes Oscar to a cemetery to watch a macabre ritual that occurs on the fourth Sunday of each month. At 10 a.m. precisely a coach pulled by black horses appears. A woman dressed in black, her face shrouded, holding a single rose, walks over to a gravestone that bears no name, only the mysterious emblem of a black butterfly.
When Oscar and Marina decide to follow her, they begin a journey that will take them to the heights of a forgotten Barcelona, a world of aristocrats and actresses, inventors and tycoons - and to a dark secret waiting in the mysterious labyrinth beneath the city streets.
