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 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.

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.

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.

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.

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.

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.