A snow storm blankets the city. Mac's "little sister", Chloe, runs away from home to spend Christmas with her. Meanwhile, Chegwidden cannot get a flight to Italy to spend Christmas with his daughter and as a result, puts a bit of a damper on Bud and Harriet's plans to bring Christmas cheer to children at a local hospital. As for Harm, he is at loose ends, and passes the time by taking on the case of a Navy psychiatrist accused of driving under the influence. He finds himself drawn to her and confides that his usual custom was to spend Christmas Eve at the Wall, with the spirit of his MIA father.
