Brad and Kate, a happily unmarried couple, look forward to spending Christmas by themselves on a sunny vacation. However, when a dense fog grounds all flights from San Francisco, their exotic trip is canceled. To make matters worse, their families see them on a televised news report about the airport shutdown, forcing them to confront a series of awkward holiday visits they have long avoided. Brad and Kate, who both come from divorced families, reluctantly agree to visit each of their parents' homes in one day, making four separate Christmas gatherings.

At Brad's father’s house, old family tensions resurface, and Brad's competitive brothers waste no time humiliating him. At Kate’s mother’s, a similarly awkward reunion ensues as Kate reencounters her childhood insecurities and her mother's flirtatious nature. As the day progresses and they face the distinct quirks and conflicts of their extended families, both Brad and Kate start to question their own relationship and where it may be headed. Each visit forces them to confront buried feelings and personality traits they have managed to avoid, paving the way for revelations about themselves and each other.