High school was hell for Marni (Kristen Bell), so she is horrified to learn that her brother's fiancee is Joanna, the nemesis of her teen years. Marni intends to expose Joanna's evil side to her family, but the situation really explodes with the arrival of Joanna's Aunt Ramona (Sigourney Weaver), who was the high-school rival of Marni's mother (Jamie Lee Curtis). When both older women revert to their teenage personas, the result is extreme wedding turmoil.