As the episode opens, a man visits his grandson for Christmas in Seattle. He dresses up as Santa Claus, but is pulled up the chimney and slaughtered by a mysterious figure. One year later, Sam and Dean Winchester pose as FBI agents to investigate a disappearance in Ypsilanti, Michigan. The discovery of a bloody tooth in the fireplace leads Sam to suspect that an evil version of Santa—many world lores tell of those who punish the wicked during Christmas—is at work. As the brothers search the town and debate about whether to celebrate Christmas that year—Dean insists while Sam refuses—another man is taken by a Santa-dressed being. Upon investigation the following day, Sam notices that both families have the same wreath over their fireplaces. The wreath is found to be made of meadowsweet, an herb often used in pagan rituals to lure gods to a human sacrifice, which leads Sam to believe that they are dealing with Hold Nickar, the god of the winter solstice. Dean later admits that he wants to celebrate Christmas since it will be his last chance to—his demonic pact with a demon in "All Hell Breaks Loose, Part Two" only left him with one year to live. Sam responds that he cannot sit around celebrating and pretending that everything is okay while knowing that Dean will not be alive the next Christmas.
Further investigation and research lead the brothers to Edward and Madge Carrigan, an apparently perfect couple whom Dean later refers to as "Ozzie and Harriet"; the makers of the meadowsweet wreaths, the Carrigans lived in Seattle a year prior. Realizing that they are actually pagan gods, Sam and Dean break into their home, finding human remains in the basement. However, they are captured by the Carrigans and tied to chairs in the kitchen. The gods reveal that they have been attempting to blend into human society, reducing their annual sacrifices to only a few. They begin preparing Sam and Dean to be sacrificed, but are interrupted by a neighbor at the front door. When the Carrigans return, they find that the brothers have broken free. Knowing that the gods can be killed by evergreen wood, Sam and Dean stab them to death with branches of the Christmas tree. Later on, Dean is surprised to find that Sam has decorated their motel room with Christmas paraphernalia. They exchange gifts, all which were bought from the local gas station, and happily watch a football game on TV.
Throughout the episode, flashbacks depict a young Sam and Dean on Christmas Eve of 1991; with their father out on a hunt, the brothers are staying alone in a motel room until he returns. As Sam wraps an object he obtained from Bobby Singer as a present for his father, he begins to question Dean about what their father is doing. Although Dean brushes him off, Sam reveals that he has read their father's hunting journal. Dean acquiesces, and confirms that their father hunts monsters. This revelation terrifies Sam, who is afraid that the monsters will come after them. Later that night, Dean wakes Sam up and claims that their father briefly returned and left presents. When Sam's gifts end up being a Barbie doll and a sparkly baton, Dean admits that he stole them from a nearby house. Despite this, Sam appreciates what Dean tried to do for him, and gives him the gift meant for their father—the amulet necklace that Dean has worn ever since.
Warner Home Video included the episode on both the Supernatural: The Complete Third Season DVD set, released on September 2, 2008, and the Supernatural: The Complete Third Season Blu-ray set, released on November 11 of the same year.
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