This documentary explores the lives and creative partnership of the brothers Angela and Luciana Giussani, who together created the iconic Italian comic book character Diabolik in the early 1960s. It traces how two women from Milan conceived and developed one of Europe's most enduring and influential antiheroes, a master thief operating in a shadowy fictional world. The film draws on archival material and interviews to examine both the cultural impact of the character and the remarkable story behind his origins.