"Forbidden" is the second volume of the novel by the Spanish writer Benito Perez-Galdos. This book continues the love story between Sisi and Faustinilla, which intersected with complex political events and social vicissitudes of Spain at the end of the 19th century. The author depicts the tragic outcome of this story at a crucial time of his era, revealing the inner conflict of the main characters and the ideals they pursue. "Forbidden" is not only love and revolutionary ideals, but also an image of Spanish society at the end of the 19th century, which is looking for a way to its own future.