Kate (Reese Witherspoon) and Brad (Vince Vaughn) are a happily unmarried couple who avoid spending Christmas with their families at all costs and instead travel to exotic locales. But when they find themselves fogged in at the San Francisco airport and their flight to Fiji cancelled, they have no choice but to spend the holiday with their divorced parents and the rest of their dysfunctional relatives. From his wrestling brothers and cradle robbing mother to her oversexed grandmother and perfect sister, the couple is forced to face their worst nightmare head on. Kate and Brad's greatest fears are realized as their families share their most personal secrets.