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 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.

When Edina's father dies, a grief-stricken Saffron is horrified by her mother's apathy. However, once she realises her own mortality, Edina decides to buy expensive artwork, which she plans to leave behind when she dies. Marshall stops by with his new grief-counsellor girlfriend, Sondra, who panics upon discovering that the corpse is to be placed in Edina's living room for the wake. Despite being banned by Saffron from attending the funeral, Edina shows up anyway, taking Patsy along. At the cemetery, Edina stumbles drunkenly into her father's grave and Patsy falls into another open grave nearby. No one offers to help as the two struggle to climb out.

Edina & Patsy go on holiday in France, where they find themselves staying in a rustic cottage, instead of the château they were expecting. There is no food or wine, and the duo are constantly disturbed by an old Frenchman whose French they cannot understand. They are later rescued by Saffron, who arrives with supplies. Bubble comes along to deliver an urgent message concerning Edina's home decorating business, but she forgets about it. When Saffron reminds Bubble about the message, Edina panics and rushes to return home. The old Frenchman stops by again and repeats his message to Bubble, who understands perfectly that Edina and Patsy have been staying in the wrong place, and were expected in the château down the road. Later, customs detains the group when a suspicious white powder is found in Patsy's luggage, but they are freed when the powder turns out to be a harmless substance. Patsy, instead of being relieved, is horrified as she realises she actually enjoyed playing ping-pong.

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.

Patsy helps Edina break in her new isolation tank upstairs, while Saffron works with classmates on a presentation for her sixth form college's open day. Edina is left feeling useless after Bubble, now a dedicated professional, takes charge of the office. She takes a sudden interest in Saffron's presentation and begs to be invited to the open day. When Saffron vehemently refuses, Edina throws a tantrum and threatens to adopt a Romanian orphan—to the point of instructing Bubble to send over a selection of babies so she can pick one. She then frantically tries to cancel the deal, but it is too late. Saffron eventually allows Edina to attend the open day. However, the presentation is interrupted as the babies arrive and start wailing, angering Saffron. Edina then wakes up in a panic, still in her isolation tank, and realises it was all a dream.

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.

Edina and Patsy travel to Marrakech for a photo shoot. They are accompanied by Saffron, who is interested in studying the local indigenous peoples for school. There, Edina and Patsy meet up with an old friend, Humphrey, who sexually harasses Saffron. At dinner, it is revealed that in the 1970s, Patsy spent a year living as a man until "it fell off", according to Edina. The following day, during a shopping trip to an outdoor bazaar, a spiteful Patsy decides to sell Saffron to white slavers. Edina and Patsy later go to the photo shoot location, but when no one shows up, they end up lost in the desert. After wandering around for a day or two, the pair are rescued as they stumble upon Saffron, who is wearing a burqa. They spend the last few days of their trip drugged and unconscious, while it is implied that Saffron had a secret dalliance with Humphrey's houseboy.

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.

Edina collects Saffron from prison, where she served two years for (unknowingly) providing asylum seekers with forged passports. Saffron later invites a former cellmate, Baron, to the house, but it is soon revealed that Baron was once Patsy's drug dealer and Patsy still owes her £50,000; Baron refuses to leave until the debt is repaid. In order to obtain the money, Saffron convinces Patsy to claim her pension, forcing her to own up to her actual age. Realising she has no official documents, Patsy begins to question her own existence until Mother presents Patsy's old Post Office savings book. After going to the benefits office with Edina, Patsy successfully pays off her debt to Baron.

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.

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.

Edina frantically organises her cluttered house in order to host old friends Bettina and Max, who were once obsessed with minimalism. Feeling ignored by Edina, Patsy leaves in search of another lunch partner. When Bettina and Max arrive, Edina is disappointed to learn that they are now the hysterical, neurotic parents of a newborn baby. As the couple wreak havoc, Edina quickly leaves the house. At a restaurant, Edina and Patsy compete against each other by attempting to befriend famous people: Patsy invites herself to lunch with Britt Ekland and Zandra Rhodes, while Edina forces her client Lulu to have lunch with her. Both lunches end awkwardly. Back home, while Saffron and Mother comfort Bettina, they hear Edina and Max having sex over the baby monitor. After the couple finally leave the intended result of Edina's fling she and Patsy make peace.

When Saffron berates Edina for being lazy and incompetent, Edina and Patsy decide to impress her by booking her favourite French film star, Jeanne Durand, to perform at the Royal Albert Hall. However, they are dismayed when Jeanne refuses to sing aloud and instead merely mouths the lyrics. As a solution, Jeanne lip-syncs to Bubble's vocals on the night of the concert.

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.

After awakening with a hangover, Edina 'Eddie' Monsoon frantically prepares to launch a major fashion show. Meanwhile, her unsympathetic daughter, Saffron—whom Edina had promised to quit drinking—constantly reprehends her mother's unhealthy habits. Edina's best friend, Patricia 'Patsy' Stone, arrives to accompany her to work. At the office, Edina's assistant Bubble reports that one of the main models, Yasmin Le Bon, has dropped out, while Princess Anne has replaced Princess Diana on the guest list. Edina subsequently manages to cajole several B-list celebrities into attendance, turning the show into a rousing success. Later that night, Edina and Patsy indulge in a drunken bender—much to the disgust of Saffron, who locks Edina out of the house. The next morning, Edina and Patsy trick Saffron into believing that Edina is going to check into a rehabilitation clinic.

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.

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.

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.

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.

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.

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, who now runs a television production company, is slated to make a guest appearance with client Twiggy on Richard and Judy's morning television show. Patsy has been injecting her face with Parralox, a Botox-like substance, in order to freeze her wrinkles. Edina is persuaded by Patsy to try Parralox as well, but she awakens the next morning with a paralysed face. In addition to costing Saffron a government job, Edina is replaced by Katy Grin, her new business partner and Bubble's cousin, for the television appearance.

Patsy has booked Saffron's baby Jane (Lola) for a photo shoot with Jean-Paul Gaultier. Gran usually babysits Jane on Thursdays, so that Saffron can go out with John. But Gran does not come this Thursday, because Edina has banned her from the house. So Saffron and John are stuck at home, and Patsy can not take the baby to the photo shoot. Patsy and Edina prey on Saffron's insecurities and tell her that John will lose interest in her, Saffron bursts into tears and agrees and asks Edina to look after Jane while she goes out with John. Edina and Patsy plan to take the baby to have a photo shoot at the London Zoo. Saffron returns and finds out they took the baby out against her wishes and Edina explains that she has bonded with Jane, however it is later discovered that Edina has brought home the wrong baby.

Saffron grows impatient with Edina's unwillingness to have their kitchen remodelled after Patsy accidentally burnt it down. Edina's obsession with finding a particular door handle for the kitchen leads her and Patsy to New York City. After a shopping spree, Patsy persuades Edina to have her navel pierced. Edina finally finds and photographs the door handle at the Four Seasons Hotel. Upon returning home, Edina not only fails to notice that Saffron has had the kitchen refurbished in her absence, but learns that she has forgotten her daughter's birthday.