In Chapter 8, when you need to make Aerith the flower wagon, talk to the boy in the fountain area of Midgar. He will say that his mother is missing and never came back. Go to the Sector 1 Train Platform, and the mother will be standing by the wall when you walk in. Ask her why she is abandoning her son, and answer "A mother without honor is nothing but a monster." Then, go back to the boy in the fountain area, and you will be in the Angeal Club.