The guy in it is new to the 'rich' area and is being introduced to the other people who live in the apartments and socialise together. Can't remember how he meets the girl, but she lives in a room in the poor area and shares with a sick female....possibly older, but not sure. They all struggle for food, etc, and he tries to help look after the sick female. The male and female fall for each other.
I think there's another man...older maybe...who helps get food and clothes for the poor people.
At the end, lots of people go somewhere else, where an older couple are waiting to lead them to a new land/place. To get there, they have to pass through a cave/dome, but they can never come back. At the edge of it...last minute he/she changes their mind, I think, and they stay behind. Possibly to keep helping others.