The film opens with Regan (Kirsten Dunst), a miserable careerist in her early thirties, having lunch with her longtime friend, Becky (Rebel Wilson), who reveals that she's getting married to her boyfriend, Dale. Although secretly jealous and embittered by the fact that her "fat friend" is now engaged, Regan notifies their two other friends, the sardonic cocaine addict Gena (Lizzy Caplan) and the rowdy party girl Katie (Isla Fisher).