Mona, a self-reliant record executive, is set to move into the penthouse apartment that her father has promised her. Her plans come to an end when she learns her spoiled half-sister, Dee Dee, lay claim to the same apartment.
Dee Dee attempts to get closer to Mona by planning a joint birthday party. Meanwhile, Dee Dee unwittingly reveals that Phyllis lied to Mona about things that have shaped her world view since she was a child.
When Mona gets on Dee Dee's case about leading a privileged existence, Dee Dee decides to prove to her and herself that she can survive in the real world by landing a job at a waitress. Meanwhile Phyllis encourages Mona to go to a dating service to find a good man .
Spencer and his new girlfriend Olivia have sex, and Spencer reveals she might be pregnant because they didn't use protection. Mona and Dee Dee give him a talking to about his mistake and encourage him to get tested, too .
Mona goes on a date with a writer for a music magazine but does not know the conversation is on the record. She tells her true feelings about one of the Delicious artists and when it gets published, she gets fired.
Feeling vulnerable after learning of another mugging around her apartment, Mona decides to take a self-defense class. Dee Dee reluctantly agrees to go with her and ends up getting hurt when Mona flips her.
Mona has intimate dreams about Spencer, but leads Dee Dee to believe that she had a lesbian fantasy dream. Dee Dee sets Mona up on a date with a woman.
Mona asks Spencer to pretend to be her boyfriend at a wedding to impress a past high school rival. With the help of Adam, Spencer realizes his feelings for Mona may be more than just as a friend.
Big Dee Dee gets Dee Dee a jacuzzi as a graduation present and it's disturbing Mona and the other tenants. Mona and Dee Dee quarrel until Charles has a heart attack.
