30 Years of Darkness tells the incredible story of Manuel Cortés, nicknamed the "Mijas mole." At the end of the Spanish Civil War, the nationalists closed all the borders, and going underground was the only option for hundreds of people who wanted to escape Franco's repression. For decades, they lived hidden under the floors or behind the walls of their own homes, only too aware that they could be discovered and murdered at any moment. Manuel Cortés, the former socialist mayor of the southern Spanish village of Mijas, was one of them. After a failed escape attempt, he decided to hide in a cramped space in his father's house. What was intended as a temporary solution, a place he would stay for only a few months, turned into a prison where he would spend the next 30 years of his life. Accompanied by archive footage, a historian, a journalist and one of Cortés's granddaughters talk about this dark period in Spanish history and the price Cortés paid to save his own skin. Cortés's experiences are rendered in hand-drawn animations that express the sense of fear and isolation felt by him and those who suffered a similar fate.