Mona, a self-reliant record executive, is set to move into the penthouse apartment that her father has always promised her. But her plans of getting settled in her new apartment soon come to an end when she learns that her spoiled half sister, Dee Dee, and Dee Dee's overbearing mother also lay claim to the apartment. The sisters' relationship is further strained when Dee Dee inadvertently attracts a man whom Mona was pining for.

Mona's music-video shoot for a rapper may end in disaster when he refuses to leave the dressing room—until he meets Dee Dee. While Mona is pleased with the rapper's newfound enthusiasm for the shoot, she soon begins to worry that he's using Dee Dee.

Dee Dee persuades Mona to attend a banquet that's being held in honor of their father, but the experience reminds Mona that she's the odd one out within her dad's ""new"" family.

Dee Dee is smitten with her new beau, but the romance sours when she learns that he and Mona dated in high school. Although Mona gives her blessing to the union, she soon changes her mind.

Dee Dee invites Mona to a ""girls night"" with her friends, but Mona instantly feels out of place amidst the ritzy women. When Dee Dee gives Mona an expensive purse, Mona deduces that her half-sister is trying to make her over. Meanwhile, Spencer is attracted to one of Dee Dee's friends.

Mona and Phyllis attend Thanksgiving dinner at Big Dee Dee's, where Mona's grandmother is the guest of honor. But Dee Dee becomes jealous when she learns the older woman showers Mona with affection. Meanwhile, Phyllis and Big Dee Dee make a deal; and Spencer blurts out one of Mona's secrets to her mother.

When Mona and Dee Dee set Spencer up on blind date with a woman they met from the gym, Spencer falls for her hard and fast. But when Mona finds out the girl is only using Spencer to get back at her ex, she tries to warn him -- only he thinks Mona is jealous.

When Dee Dee becomes frustrated with Neil because he does not seem interested in getting intimate, he divulges that he is celibate. Meanwhile, Mona is under pressure at work and takes up smoking again, but she is too embarrassed to admit it and tries to hide it from her family.

Spencer thinks that he has gotten a girl pregant and Dee Dee and Mona force him to get an AIDS test.

Mona fears a lonely Valentine's Day, but her tears may be for naught when two men from her (recent) past both ask her on dates. Also, Dee Dee is miffed that Neil would choose work over her. Meanwhile, Big Dee Dee is angry with her husband, who also chooses work over her.

When Mona mistakes a dinner date with a handsome reporter as a personal affair, she unwittingly gets quoted in a music magazine saying disparaging things about one of her music label's artists that ends up getting her fired. Meanwhile, Dee Dee utilizes her law school knowledge to try to get the story retracted.

While Mona struggles to find work after poisoning her reputation in the record industry, the reporter whose article got her fired tries to make amends and sets up a meeting for Mona to plead her case to Big Phat Slim Jim, the artist she disparaged, in hopes of getting her old job back. Meanwhile, Mona's family and friends offer their encouragement and support in their own special ways during her difficult job search.

In a strange reversal of fortunes, Dee Dee's charmed life seems to hit an unlucky streak at every turn while, ironically, the usually pessimistic Mona's life becomes auspicious from one moment to the next. When Dee Dee starts doubting herself after failing her assigned mock-court competition at school, with Mona's help she manages to regain her waning confidence by confronting a crooked businessman.

Mona dates a hunk whose looks almost compensate for his lack of brains. As a result, she tries to hide him from her friends and family, but the effort is for naught when they're invited to her father's dinner party for a U.S. senator.

Mona drags Dee Dee to a self-defense class, where she accidentally hurts her little sister while practicing a back flip. Overwhelmed with guilt, she waits on Dee Dee hand and foot, unaware that Dee Dee's milking the injury.

Mona becomes antsy about her friendship with Spencer after she has a romantic dream about him. Meanwhile, Dee Dee---who thinks the dream was about a woman---introduces Mona to a lesbian friend of hers.

When Mona has Spencer masquerade as her beau at a friend's wedding, Spencer realizes that he has romantic feelings for her, and has had them since college. Meanwhile, Dee Dee dumps her boyfriend when she learns he has matrimony on the mind.

For Mother's Day weekend, Big Dee Dee and Dee Dee vacation at an exclusive spa. Not to be outdone, Phyllis and Mona do the same, and end up in the room next door. The weekend quickly goes from weird to worse when Dee Dee blurts out that she wishes her mom was more like Phyllis.

The gals' already tenuous friendship spirals toward dissolution when Dee Dee celebrates the end of her school year by hosting a raucous celebration that keeps Mona awake all night. Things get worse when Dee Dee installs a hot tub, which floods Mona's apartment. Stepping in to mediate, their father, Charles, reminds them that ""like it or not, we're family."" But the squabbling continues, until a medical emergency involving their dad arises.

Dee Dee and Big Dee Dee plan a ""surprise"" party for Charles and Big Dee Dee's 24th wedding anniversary. While putting together a slide show, Dee Dee discovers that there are very few photographs of Mona with their father. She feels sorry for her sister and makes several attempts to cheer her up (first creating fake photos of the two, then trying to set up a lunch date for Mona and Charles), but only angers her further. Mona explains that she had accepted the fact that she and her father didn't have the closest relationship, but Dee Dee is inadvertently opening the wounds. Phyllis produces evidence that proves Charles wasn't quite as distant as it seems. Spencer develops an attraction to Camille, a photographer working with Delicious Records artists. Adam constantly tries to alert Mona about Spencer's feelings for her. He finally tells her the truth, but they discover that Spencer is involved with Camille. Meanwhile, Dee Dee becomes annoyed when her ""summer fling"" starts to get

Dee Dee takes a pregnancy test, although Mona feels that she might be overreacting (her period is only a day late). Before Dee Dee can check the results, her mother bursts and demands to use the bathroom. Big Dee Dee also takes a pregnancy test, which turns out to be positive. She is startled, but she and Charles quickly accept the news. Big Dee Dee gets to rub her pregnancy in the face of Phyllis, who had believed Big Dee Dee was going through menopause. Mona is upset to realize that Spencer has been seeing Camille for some time, but hadn't confided in her. He claims that he wanted to keep quiet until he knew the relationship could last. Phyllis chastises Mona for letting ""her"" man get away, while Adam refuses to believe that Spencer is over Mona. He insists that he is happy with Camille, adding that Mona would never want him anyway. Mona patches things up with Spencer and says that she is very happy for him.

Aspiring politician Ron Brown shows up at Mona's door in search of votes, and takes a liking to her. Phyllis quickly pushes him to ask her out, and they agree to a date. Mona then learns that Big Dee Dee recently arranged a date for Dee Dee and Ron, who have been friends since childhood. The sisters are unsure about dating the same man, but their mothers insist that it will be all right (as it is unlikely that both will be compatible with Ron). Phyllis and Big Dee Dee treat the whole thing as a personal competition. Mona and Dee Dee like Ron, but decide that he isn't worth the potential damage to their relationship. They agree to do the ""mature"" thing and stop dating Ron, but each keeps seeing him behind the other's back.

Mona tells her friends and family that she doesn't want to celebrate her birthday, as she would rather spend the day alone in quiet reflection. However, she soon becomes extremely bored. She is relieved when Big Dee Dee shows up, although she has actually forgotten Mona's birthday and is just there to see Dee Dee. The two go down to the laundry room in pursuit of Big Dee Dee's dog, and wind up trapped when an earthquake hits. They share a picnic lunch and have a revealing talk about their relationship. Meanwhile, Phyllis tracks down Charles to try to convince him to help buy a car for Mona's birthday, and they wind up stuck in an elevator. The earthquake also traps Dee Dee, Adam and Spencer in an upscale store as they shop for Mona's gift. Everyone is embarrassed when Spencer has a panic attack after the earthquake.

After Dee Dee loses her old room to the baby and Big Dee Dee misses several appointments, Dee Dee begins to worry that the baby is forcing her out of her parents' life. She suffers from so much stress that she has a breakdown and hears a doll talking to her. Mona recommends that she make an appointment with Phyllis to discuss her problem. She says that she feels as though she is the only one who is worried about the way the baby will change her life. Phyllis assures her that her reaction is perfectly natural and that she should air her concerns with Big Dee Dee. Before she gets around to it, Big Dee Dee admits to her own anxieties about the child's birth, and thanks Dee Dee for her support. The conversation reassures Dee Dee about her importance in her mother's life. Meanwhile, Spencer continually cancels on Mona because of plans with Camille. She looks to Adam to take his place, but Adam isn't too thrilled about this.

Hoping to prove herself to her father, Dee Dee goes against his wishes and tries to personally handle a tenant who has failed to pay rent for the last few months. She must come up with a new plan of attack after the man retaliates by threatening to expose several building code violations involving Dee Dee's apartment. Meanwhile, Mona reluctantly takes her mother out on the town. She feels crowded when Phyllis begins showing up regularly at her hangout and playing matchmaker for the patrons.