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.
When Dee Dee befriends Spencer, Mona becomes concerned that her sister is stealing her best friend. Meanwhile, Mona leads Dee Dee and Spencer into believing she is still dating Brian the exterminator even though he hasn't call her after their very hot date.
Dee Dee attempts to get closer to Mona by planning a joint birthday party, reminding Mona of bad memories from their childhood. Meanwhile, Dee Dee unwittingly reveals that Phyllis lied to Mona about things that have shaped her world view since she was young; and, as a birthday gift, Phyllis finally tells Mona the truth.
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.
In an attempt to win Mona's respect and stop living off her father's largesse, Dee Dee takes a job as a waitress. Meanwhile, Phyllis persuades Mona to give a video-dating service a try.
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.
While at a club with Spencer, Mona meets the hunky Miles. They hit it off, but their budding romance quickly trips up over matters of taste: For one, she enjoys Dawson's Creek, while he prefers BET. After a night on the dance floor, where Mona displays her lack of rhythm, Miles breaks up with her for not being ""black enough."" In an attempt to win him back, Mona remakes herself into what Dee Dee calls ""a Nubian disco queen.""
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.
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.
