Plot
Struggling siblings Alice and Paul siblings live far from their family. He is a gay rehab center worker in a relationship with his live-in partner Dominic, and becomes neurotic when Dominic wants to open to other partners. Alice is an executive assistant at an architectural firm, having an affair with her married boss Jonathan. Her hopes that he will leave his wife are dashed when she discovers his wife has just had a baby.
Both siblings are estranged from their mother Donna, and their older half-sister Eloise, from Donna's first marriage to Henrique, a wealthy French-British playboy. She divorced him after discovering his infidelity. Donna later marries Bill and has a seemingly happy marriage, producing Alice and Paul. Eloise spends the summers with her father in Britain and never really connects with her half-siblings.
Years pass, and Eloise, now wealthy through her father's influence, becomes engaged to Ollie. Hoping to bridge the gap with her American family, she invites them to her wedding. The now-widowed Donna enthusiastically accepts, while Paul and Alice are less enthused, resentful of their mother's tie with Henrique. However, Eloise's well-meaning gesture to pay for Alice's very expensive hotel room upsets her, causing further resentment.
After Paul loses his job for empathizing with a patient, Dominic suggests that they save money by staying with Alcott, Dominic's gay older college professor. He tries to be open-minded when Dominic and Goulding engage in sexual activity and attempt to draw him into it, but then he leaves in a huff.
Meanwhile, Donna reconnects with Henrique, having sex with him. He hints at wishing to reconcile with her, which delights Eloise but infuriates Paul and Alice.
There is a subplot involving Alice and Dennis Bottoms, a Nebraskan whom she meets on the plane and with whom she later has a fling with at the hotel. She spends a lot of time with him and enjoys his company, but when she believes Jonathan is on his way to London, she falsely confesses to Dennis that she is in a relationship that she is ending.
Receiving another text from Jonathan saying he has arrived for the rehearsal dinner, she discovers it is actually Jonathan's wife, after having suspected Jonathan's infidelity. She tries to fight with Alice, and Dennis tells her he is done with her. A drunken Paul appears, having just broken up with Dominic. Discovering Henrique kissing a much younger woman, he punches him and then urinates on his shoes.
Fed up with the drama, Eloise throws all three out and disinvites them to the wedding, but first she lashes out at Paul misguided anger with his mother. When Donna had removed all traces of Bill's existence after his death, yet kept a photo of Henrique. Paul discovers she threatened to divorce Bill if he openly showed his inacceptance of Paul's homosexuality. This likely lead to the cooling of their relationship in Bill's final years. Realizing that Donna had been protecting him, Paul weeps bitterly and makes up with her, as does Alice.
Although Dennis is upset at Alice's deception, he drives them all back to the hotel after the trio are booted from the dinner and jailed. The next morning, as the trio prepare to fly back home, a frantic Ollie finds them as he cannot find Eloise anywhere. On a hunch, Donna correctly guesses she is at a Taco Bell restaurant (a childhood indulgence allowed by Donna but forbidden by Henrique) gorging on fast food.
Alice persuades Donna to let her talk to Eloise alone. She confesses she held a grudge against Eloise when she did not come to her aid after she suffered a miscarriage. Eloise apologizes, confessing that she stayed away because shortly before that she had learned that she can never conceive—a secret she has yet to share with Ollie—so was not emotionally available to support her sister. They make amends at last and also persuades her to be honest with Ollie.
A year passes and the siblings are together again with Donna, this time much more happily. Ollie and Eloise are still a couple, having adopted a baby, and Dennis has forgiven Alice and they are back together.
