This is a pretty long act. It covers Clara's childhood at the beginning of the novel to the military coup, when those who supported the Socialist Party have to go into hiding or, like Alba, help others escape persecution. There's no turning back now.
This act covers Alba's subversive activities, Pedro Tercero's hideout in the big house on the corner, Esteban Trueba's growing discomfort with the new military regime, and Alba's secret reunion with Miguel. It lasts until the secret police break into the big house on the corner in the middle of the night and burn the family's books and documents in a huge bonfire. They arrest Alba in the middle of the night and take her to a secret prison. The spirits don't come to her aid – it seems no one can help her now.
In Act III, Esteban Trueba goes to Tránsito Soto for help as a last resort. He begs her to use her influence to have Alba released. She does, thus managing to repay Trueba the favor she's owed him for fifty years. Alba is transferred to a women's concentration camp, and then released in a dump on the outskirts of the city. She makes her way home and is reunited with her grandfather. They restore the house and write this novel. Esteban dies at peace, with the help of Clara's spirit. Alba forgives her torturers and tells us she's expecting a baby. Resolution feels good.