As a teenager Marni (Kristen Bell) was the kind of girl no guy would go near and would be tormented by the mean girls, and no one was meaner to her than Joanna (Odette Annable), the head cheerleader. Years later, she's a successful woman with a good job. When she goes home for her brother's wedding, she discovers that her brother (James Wolk) is marrying Joanna. And he doesn't know what she did to Marni. When they meet, she wants Joanna to apologize for the way she treated her but Joanna feigns ignorance. When Marni tells her mother, Gail (Jamie Lee Curtis), about her and Joana, Gail tells her to try and put it behind her. But when Gail meets Joana's aunt Mona (Sigourney Weaver), it turns that she's her old friend Ramona who was her best friend in high school whom she had falling out with with years ago, and Gail is unaware what caused it. Gail feels like Mona is trying to rub her success in her face. When Marni learns that Joanna does remember her she sets to expose her to her brother.

romcom