Upon discovering that Serge is gay and living in New York, Edina is thrilled to reunite with her long-lost son as she plans a trip to New York Fashion Week with Patsy—despite Saffron's objections. In exchange for Serge's contact information, Edina and Patsy are forced to get married by a counsellor at an LGBT drop-in centre where Serge volunteers. Edina finally locates Serge, who works in a second-hand bookstore and, to her surprise, is essentially the male equivalent of Saffron. Despite initially rebuffing Edina's attempts to reconnect due to unresolved issues, Serge is convinced by his flamboyant boyfriend, Martin, to spend the day with her. Edina, Patsy, Serge and Martin attend Fashion Week and later go on a bar crawl. The night ends with Edina and Patsy getting arrested after accidentally setting a bar on fire. The pair return home after Saffron posts bail, and Edina reveals that she has disowned Serge in favour of Martin, whom she has "adopted".

Edina joins a New Age commune, but she struggles to fit in and quickly becomes bored. Patsy finds herself disillusioned with her new job in New York due to creative differences with her co-workers. Saffron settles into university life and Mother spends her days at the Monsoon house, drinking champagne and ordering items from the shopping channel. After realising that their lives are not the same without each other, Edina and Patsy happily reunite on top of Carnegie Hall Tower before returning to London. Back home, Mother has been arrested for squatting and credit card fraud. A flashforward to 25 years into the future provides a glimpse into the lives of Edina, Patsy, Saffron and Mother.

Edina becomes frustrated when she loses a prestigious PR award to rival Claudia Bing, despite having bribed the judges. Worried about her dwindling career, Edina works on a campaign in hopes of upstaging Claudia. Meanwhile, Saffron becomes romantically involved with Gerard, her psychology lecturer, until she discovers that he is married with children. In a rare occurrence, Edina comes to Saffron's aid by punching Gerard in the face. At an industry luncheon, Edina's speech is stolen, prompting a drunken rant against the bastardisation of the PR industry, which proves a success. When Edina and Patsy attempt to retrieve the speech, the duo awaken the next morning on a trash barge headed for Ostend.

Edina discovers that both Marshall and Justin have cut off their alimony payments. After Saffron conspires with Edina's accountant, Edina is led to believe that she is poor, and reluctantly agrees to reduce her expenses. However, during a trip to the supermarket, she and Patsy fill three trolleys with groceries and steal a crate of champagne. Edina's "smaller" Alfa Romeo car is impounded outside Harvey Nichols, and the pair are later arrested for driving under the influence and several other charges, including assault and shoplifting. On the day of the trial, Edina goes on a rant in an effort to justify her actions, to no avail. In addition to a large fine, she and Patsy are sentenced to community service in a nursing home.

For the first time ever, Edina has agreed to stay home and spend Christmas with the family. Edina typically goes overboard by buying a huge tree and tons of gifts. Patsy is very upset that she cannot go away on vacation with Edina as they do every year, as she hates Christmas. Patsy has a flashback of unpleasant Christmas memories of her childhood. Someone somewhere sticks a pin in a Patsy voodoo doll, and she collapses in pain beneath the Christmas tree. Although Edina and Saffron ignore her, John insists that Patsy needs to go to the hospital. Once at the hospital, the doctors tell Edina that Patsy is very sick and that she may die. Edina and Saffron return to the house to continue their Christmas celebration. In the middle of the night, Patsy's estranged sister Jackie arrives to visit her. The following day, Edina and Saffron drop by only to learn from a nurse that Patsy has died, only they find out that it turns out to be Jackie instead.

As Edina and Patsy prepare to attend an underground rave on New Year's Eve, they receive an unexpected visit from Patsy's long-lost older sister Jackie. Patsy insists on taking Jackie along to the party, much to Edina's dismay. However, Patsy is disappointed to learn that Jackie is no longer the jet-setting, drug-addled party animal she used to be. Now homeless, Jackie asks Patsy if she could stay with Edina until she can raise money to open a shelter for stray cats and dogs. After helping Jackie loot Edina's bedroom for valuables she can sell to raise money, Patsy throws her out of the house, but it is too late to go the party a frustrated Edina has fallen asleep in the sitting room, surrounded by her family as the clock strikes midnight.

Edina decides to rent out her house to Michael Douglas during the Summer Olympics, hoping it will lead to prestigious A-list parties, even though Patsy—who now needs incontinence pants—no longer shares Edina's penchant for partying. However, Bo and Marshall arrive instead, after Michael gave the couple his party invitations. Frustrated with her dwindling social life, Edina happens upon one of Michael's invitations, allowing her and Patsy to attend a pre-Olympics party. The pair are eventually escorted out after Edina harasses Stella McCartney.

Saffron's first play, Self-Raising Flower, which details her troubled relationship with Edina, is due to open in a local theatre. Worried about being portrayed in a negative light, Edina unsuccessfully attempts to sabotage the play. As the rest of the family gather for the opening night, Saffron decides to invite Edina, who reluctantly attends with Patsy. The two are surprisingly amused by the play—despite the fact that Patsy is played by a man. The play becomes a roaring success due to being perceived by the cast and audience as a comedy, as opposed to the tragedy Saffron had intended.

Patsy convinces Edina to hire two male prostitutes (through Edina's hairdresser Christopher) for an orgy on the night of Saffron's university presentation. However, Edina is unable to loosen up, and the prostitutes are not particularly enthused, either. Patsy attempts to enliven the mood by playing a video of an orgy she and Edina attended in their youth, only to find that it has been accidentally switched with a tape of Saffron's school project. Fearing the worst, Edina and Patsy accompanied by Mother, Christopher and his drag-queen boyfriend rush over to the university, though not soon enough to prevent a mortified Saffron and her classmates from watching the orgy tape, which shows couples having sex while Edina is asleep.

Edina builds a panic room. Patsy is at her shop, Jeremy's, when Minnie Driver walks in. Minnie complains about not scoring any free stuff from other shops at Bond Street, and takes pictures of herself shopping to sell to the paparazzi. Patsy is determined to become Minnie's stylist, so she later invites Minnie to Edina's house. She has gathered racks of designer outfits with which to dress Minnie. When Minnie wants a necklace that Edina is wearing, Patsy wrestles Edina for it, and they accidentally lock themselves in the panic room. They believe they will be unable to escape for days because Patsy panicked and kept pressing the buttons on the keypad. While they are locked in, they play Trivial Pursuit over the intercom and camera with Saffron. They also discover that Minnie Driver has taken all the designer clothes. At the end, Edina and Patsy discover they were locked in for only a couple of hours.

Edina has a nightmare about Saffron's baby trying to stab her. It turns out that the face of the nightmare baby belongs to Saffron's midwife, who delights in teasing Edina about these nightmares. Edina expresses her displeasure about this baby. Saffron invites the father of the baby to the house to tell him she is pregnant. In the meantime, Edina and Patsy have organised a book club, but no one is interested in reading any books except celebrity magazines. When Edina discovers that John Johnson, the father of Saffron's baby is black, she is overjoyed, because she thinks a mixed-race baby is the greatest accessory, the "Chanel of babies." When Saffron tells John that she is pregnant, he replies that she should tell people that she is pregnant right away or people will think she is fat.

Edina's 'new' boyfriend Pete is a tape engineer who used to work at Abbey Road Studios during the time that the Beatles recorded there, and who had found some unreleased tapes. In a studio, the girls have fun and Edina sings her 'walking down the road' song she loves. There are flashbacks from the sixties where Patsy is a man and they are at a recording for the Sgt. Pepper album. Back at home, Elton John had been invited to the party to debut the Beatles tapes, but gets annoyed and leaves when he discovers he was only invited to play piano in the background. Finally, just after proposing marriage to Edina, Pete plays the tapes at the party. Instead of The Beatles, Edina is heard singing. Apparently this is because Patsy had pressed the record button on the recorder in the studio by mistake whilst she was looking for champagne in the control room, and Edina unknowingly sang over the tapes.

Saffron accepts a marriage proposal from Paolo, her pompous, controlling Italian boyfriend, to Edina's shock. Edina and Patsy travel to a ski resort in Val-d'Isère, France, but they are disappointed by the lack of celebrities in town. Later, a drunken altercation ensues when Edina points out their constant dependency on each other, destroying their chalet in the process. The next day, Edina loses control while skiing and nearly falls over a cliff. In a near-death experience, God (in the guise of Marianne Faithfull) appears to Edina in heaven, informing her that it is not her time yet. Back in London, Mother is brought home by a disguised Bo—who is hiding from Scientologists—after being mistaken for a terrorist at the airport, and realises she has forgotten to collect her American friends, Mac and Millie.

Edina decides to remodel the kitchen again, and calls up her old minimalist friends. It turns out Bettina is divorced and is clinically insane and Max is revealed to be gay. Bettina transforms the kitchen into a stairless white box, but Edina hates it. Patsy, meanwhile, develops serious health problems and walks around with an IV stand. Saffron returns from her wedding to John in Kenya and reveals that he is a polygamist. Edina and Patsy head off to meet designers Terence Conran and Kunz for inspiration. At Kunz's store, Edina claims to have seen her ideal kitchen in a previous life, so she hires a channeller. The channelling session results in so much disruption in the household that Saffron and Edina argue once again, and Edina lashes out at baby Jane in anger. Saffron has finally reached breaking point, and kicks Edina and Patsy out of the house, which is in her name. Edina and Patsy end up lounging in the stylish window display of Terence Conran's Shop.

When Saffron hires a handsome landscape gardener to redesign the backyard, Patsy recognises him as Jago Balfour, the younger brother of a wealthy acquaintance of hers, who inherited a country estate before dying of an overdose. Presuming Jago to be rich as well, Patsy goads Edina into seducing him. Edina and Jago soon arrange a dinner date, which eventually leads to a wild night of lovemaking. The next morning, Jago reveals that his brother squandered the family fortune on drugs, forcing him to sell the estate to Roger Daltrey as a fish farm, much to the horror of Edina and Patsy.

Patsy accidentally burns down the Monsoons' kitchen with a cigarette. She and Edina later plan a night out, but they decide to stick around after learning that Saffron is expecting a date, much to her chagrin. To make matters worse, Mother inadvertently locks the three women in the living room on her way to the chemist's. Edina pesters a mortified Saffron with questions about her sex life, before the trio exchange stories about their own births. Patsy—who had a neglectful mother—expresses her resentment towards Saffron due to the privileges she enjoyed while growing up, leading to a bitter dispute between the two. When Mother eventually returns home and unlocks the door, Edina and Patsy quickly leave, while Saffron's date is waiting outside. A flashback sequence shows Edina as she plans to surrender Saffron for adoption.

Patsy, who is temporarily staying with the Monsoons, becomes jealous when Edina reconnects with an old boyfriend. During one of her sporadic appearances at work, Patsy is assigned to host a fashion makeover segment on a morning television show. After clashing with the models, Patsy attempts to persuade Saffron and Mother to appear on the show in their place, telling a tale of her emotionally distant mother. Saffron agrees, on the condition that Patsy moves out of the house and does not interfere with Edina's relationship. Patsy's television appearance turns disastrous as she suddenly becomes nervous. After Patsy convinces Edina to break up with her boyfriend, Saffron lashes out at Patsy for not upholding her end of the deal.

Patsy is excited to be joining young supermodel Erin O'Connor for a magazine photo shoot in Paris. Edina and a reluctant Saffron come along for a mother–daughter fashion spread. After learning that other models from her generation will also appear in the shoot, Patsy becomes competitive and constantly ignores the photographer's directions, much to his annoyance. Meanwhile, Edina and Saffron spend an unusually pleasant day together in Paris, going shopping and dining at upscale restaurants. Edina later encourages Saffron to flash her breasts from the top of the Eiffel Tower. However, Edina's ulterior motive is revealed when a photographer appears unexpectedly and takes a topless picture of Saffron for a magazine.

Edina is none too pleased about her 40th birthday. As opposed to the glamorous, star-studded surprise party she had hoped for, Edina is disappointed to learn that Saffron has planned a quiet lunch with family and friends—including both of Edina's ex-husbands, Justin and Marshall, and their respective new lovers, Oliver and Bo, as well as Patsy and Mother. Edina behaves erratically during the party, switching between self-pity and spite, and she soon provokes Oliver, her least favourite guest, into making an angry exit. Justin and Marshall are shocked to discover that they have both been paying alimony to Edina. While Edina and Patsy sing drunkenly on a new karaoke machine, Justin and Bo secretly plot to cut off Edina's alimony.

Saffron is preparing her home birth kit. She's due to have the baby anytime, Patsy is the hostess of the Style Awards at the Royal Albert Hall. Edina helps Patsy rehearse her speech but is interrupted by Katy Grin, Bo, and Marshall. Katy talks about her work in the musical Chicago. Bo and Marshall talk about their Christian Family Creation adoption service, which is a service for busy Hollywood actresses who have no time or desire for pregnancy. Saffron and Patsy shove each other trying to get up the stairs, and then suddenly Saffron's waters break, spilling baby juice all over Patsy's expensive clothing. Saffron retreats to her bedroom with contractions. In a rare moment of support for her daughter, Edina tells Patsy she won't be able to go to the awards show. Saffron eventually gives birth to a healthy baby girl.

Unable to fit into the majority of her clothes, Edina becomes determined to lose weight. At the office, she is horrified upon learning of an upcoming visit by Penny Caspar-Morse, a thin model that used to torment Edina about her weight. Edina unsuccessfully attempts to exercise, and with Penny arriving earlier than expected, she accepts Patsy's suggestion to undergo a liposuction. After a disturbing nightmare about the procedure going horrifically wrong, Edina decides against the idea and instead puts on an oversized sweatshirt in order to cover herself up. Patsy announces that Penny is blind, much to Edina's delight. Later, Edina drunkenly rants at Penny about how she ruined her life and brags about how successful and thin she has become. However, she inadvertently reveals her weight as she grabs Penny's hands and places them on her waist.

Edina begins an ad campaign for Prince Charles' biscuits, and claims that it is "by royal appointment". she begins to associate with the wealthy socialite crowd, and buys a weekend at a country house hotel. Upon arrival, Patsy and Edina discover that nothing is in season, and the place doesn't even have any jacuzzis or massage. Patsy tells Edina that the Rothschilds were laughing at her. Edina becomes angry and determines that she will kill something, and goes out with Patsy with guns blazing in the middle of the night. They bring a pheasant back to the hotel, which Edina puts in the closet. In the morning they discover that the pheasant is still alive. Patsy tells Edina to pull its neck but Edina bonds with it and drugs it and releases it into Hyde Park. At home, Emma and Sarah bring gifts to Saffron for a baby shower, and Sarah becomes obsessed with Emma. Sarah stalks Emma, and Saffron eventually calls the police and has Sarah arrested.

Patsy becomes the subject of a tabloid sex scandal following an affair with a married MP. Edina checks into a hospital for surgery after injuring her big toe. Patsy tags along, planning to undergo a chemical peel in preparation for her interview with Hello! magazine. While anesthetised, Edina dreams that she is on her deathbed, surrounded by idealised versions of family and friends, while Patsy envisions herself looking young for her Hello! spread. Edina awakens to find that her pains were caused by a stray acupuncture needle that worked its way from her cranium to her toe. Meanwhile, a botched facelift leaves Patsy's face covered in burns. The Hello! spread is also a disaster, with the article reporting Patsy's age as 49, blaming her for the sex scandal and revealing her horrific facelift.

Edina and Patsy return home from Val-d'Isère. Upon discovering that Paolo's parents are wealthy and famous, Edina takes a sudden interest in Saffron's upcoming wedding. When Paolo's parents come to visit, his mother, Kalishia, disapproves of Saffron and refuses to allow Paolo to marry her. Patsy blackmails Kalishia into changing her mind by reminding her that they once co-starred in a Bond-inspired pornographic film. On the wedding day, Edina replaces Saffron's bridesmaid, Sarah, with Georgina, a Gucci model. When the vicar asks if there are any objections, Edina has another vision of God, who opposes the marriage. Edina interrupts the ceremony, prompting the guests to leave, while Paolo departs with Georgina. Though initially devastated, Saffron ultimately admits that Paolo was not right for her, before Edina and Patsy reveal that they are going on her honeymoon trip.