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.

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 enrolls in a boot-camp fitness programme and subjects herself to a strict diet, after being ridiculed for her weight by Katy Grin, Catriona and Fleur. Meanwhile, Patsy briefly experiments with pulling back her signature fringe for the first time in decades, and budding playwright Saffron receives a visit from Taylor, a pretentious old school friend with acting aspirations. Despite initially struggling, Edina's efforts soon pay off as she realises she has lost one stone. Proudly displaying her slimmer figure, Edina meets her friends again for lunch, but her weight loss is still not enough to deter Katy Grin's snide remarks.

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.

Bubble accidentally emails Edina's clients' details to nemesis Claudia Bing, who poaches most of Edina's clients, including Twiggy. Patsy—who has recently been diagnosed with osteoporosis—and Edina are horrified when Saffron forces them to attend a Menopausals Anonymous meeting organised by her. In order to save her business, Edina dupes Claudia into buying her TV company—which currently has no programmes—while Claudia also agrees to return several high-profile clients. Saffron has a terrifying nightmare in which Patsy threatens to impregnate herself with a vial of Mick Jagger's sperm unless she is allowed to move into the spare room.

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".