Christmas comes but once a year and when it does, happily unmarried couple Brad and Kate (Vince Vaughn and Reese Witherspoon) always go on holiday to avoid their divorced folks and gruesome siblings. But when their flight is cancelled, the pair must find the goodwill - and strength - to visit all four parents on Christmas Day. Robert Duvall, Mary Steenburgen, Sissy Spacek and Jon Voight play the embarrassment-in-laws in a festive comedy where slapstick rules over slush.