|Seattle, Washington - One Year Ago
A young boy greets his grandfather. It's Christmas eve and once the boy is in bed, the grandfather dresses up as Santa, making enough noise for the boy to wake and spy on him as he put the presents under the tree. There is a noise from the roof, and then one from the chimney. "Santa" investigates the noises when he is dragged, screaming into the chimney, watched in horror by his grandson. Sounds of munching and screams come from the chimney, closely followed by one of his bloodied boots rolling out of the fireplace.
Ypsilanti, Michigan - Present Day
It is three days before Christmas and Sam and Dean (posing as FBI Agents) are interviewing Mrs Walsh, whose husband, Mike, vanished during the night. She had heard a thump on the roof and then she heard him screaming. Sam looks around inside the house and finds a tooth in the chimney. They need to find out what dragged him up there; this is the second man who has vanished in town that month. Sam makes a suggestion to Dean that maybe it's the Anti-Santa who punishes the wicked. Not having any better leads, they find out that both men visited a local "Santa's Village" before they went missing. While they start looking around the village, Dean suggests that the two of them have a Christmas celebration this year. Sam argues that he doesn't want one.
Broken Bow, Nebraska - Christmas Eve 1991
Sam is wrapping a gift for John in newspaper and asks when John will be back. Dean tells him that John is gone on business, but Sam continues to ask questions about John and Mary. Dean loses his temper and storms out of the motel room.
Sam tells Dean that the lore about Anti-Santa is that he walks with a limp and smells like sweets. They look around and see a man dressed as Santa who fits the description. They follow him that night to his trailer and wait outside to see what happens. Dean asks Sam why he hates Christmas. Sam is saved from giving an answer by the sounds of screaming coming from inside the trailer. They barge in, only to find the man, drunken, watching a film. To cover their break-in, they start singing Silent Night, backing out slowly as the man sings along.
Inside another house, another young boy creeps downstairs after hearing a noise. Something bursts out of the chimney and stalks upstairs. A woman screams and the intruder drags someone else down the stairs in a sack. Watched by the horrified little boy, he drags the body back up the chimney. The next morning, Dean and Sam, as FBI Agents, are interviewing the woman, Mrs Caldwell. Sam mentions a wreath that he saw inside the house, the Walsh's had the same one in their house.
Sam phones Bobby who tells the boys that they are morons for thinking it was the Anti-Santa. He tells them that they wreaths are probably made from meadowsweet, a rare plant that is used as a powerful pagan ingredient. It was sometimes used in human sacrifices as the Pagan gods are attracted to it. Sam thinks it could be Hold Nickar, the god of the winter solstice. Sacrifices to him are said to lead to mild weather, such as a lack of snow in Michigan in the middle of December. The boys track the wreaths to a local woman named Madge Carrigan.
Back at the motel, they discuss Christmas again. Dean reminds Sam that this will be his last chance for a Christmas. Sam replies that is why he can't celebrate it; he isn't prepared to just pretend everything is great when he knows that by next year, Dean will be dead.
Broken Bow, Nebraska
Dean returns to the motel. Sam has found John's journal and asks Dean outright if monsters are real. Dean starts by telling his brother that they have the best Dad in the world, one who fights the monsters. Sam accepts this, but is worried that if the monsters are real, what will happen if they get their Dad. Dean promises that wont happen, but Sam falls asleep, crying.
Dean and Sam knock on the door of the Carrigans house. They are greeted by an overly nice Mr and Mrs Carrigan. However, Sam notices that the decorations inside their house are not normal, they're vervain and mint, which is, in Dean's words "serious pagan stuff." That night, the boys decide to break into the house to investigate further. At first, they don't see anything suspicious until they find the locked door to the basement. There is blood and human remains all over the place. Suddenly, the Carrigans are there, still being sickly sweet, and batter the boys into unconsciousness.
When they wake up, Dean and Sam are tied to chairs in the kitchen. The Carrigans recognize them as hunters, knowing that they cannot possibly let them go. They want to kill the boys, but insist on their rituals in order to do so. While they get things ready, they complain to the boys that they have spent the last 2,000 years trying to go from being Pagan gods into living life as humans. They're so proud of the fact that they only kill two or three people a year now, when they used to kill hundreds. Both boys are cut, their blood being dripped into a bowl. They pull a fingernail from Sam and are about to pull a tooth from Dean when the doorbell rings. It is one of their neighbors, dropping off a fruitcake.
When the Carrigans return to the kitchen, Dean and Sam have escaped. They lock themselves in the main room, desperately searching for some evergreen stakes to kill the Carrigans with. Hacking the Christmas tree to death, the boys succeed in destroying the gods.
Broken Bow, Nebraska - Christmas Morning
Dean wakes Sam and shows him the tree and presents that John has brought while he was asleep. Sam opens his presents to find Sapphire Barbie and a cheerleading baton. Dean confesses that he stole the presents from a nearby house as John couldn't make it. Sam hands over the present he was saving for John, wanting Dean to have it instead. Dean unwraps it to find an amulet in it. He places it over his head with a smile.
Ypsilanti, Michigan - Christmas Day
Dean arrives back at the motel. Sam has decorated a tree and made eggnog; he has agreed to have Christmas this year. Dean hands over a couple of presents that he bought at the local garage: skin mags and a can of shaving cream. Sam gives Dean the gifts he bought for him: candy and car oil. The two of them sit back and watch a football game on the TV.