In the town of Cityville, Jake Spankenheimer's Grandma Spankenheimer runs a small general store that stands as the last vestige of a family empire in a place where Austin Bucks and his Christmas conglomerate are reshaping how the season is lived. The new, slick approach to Christmas promises convenience, but Grandma’s stubborn hold on the store irks the ambitious tycoon, who is determined to buy it up. Enter the scheming Cousin Mel, whose greed nudges her to push a sale through by any means, even sabotaging Grandma’s famous fruitcake in a bid to sabotage Christmas spirit and sales alike.
Jake and his grandparents are among the few who still believe in Santa Claus, and their faith is reinforced when Grandma is somehow knocked over by Santa’s reindeer—an accident that marks the beginning of a troubling year. The next morning brings the chilling sight of Grandma’s missing person case: an imprint in the snow and her belongings left behind, sowing doubts and fear. Cousin Mel wastes no time in grabbing a letter Grandma had, keeping it hidden from the rest of the family as she schemes to seize control of the store.
Nine months pass with little word of Grandma, and the business continues to slide. Mel hatches a new plan to force a sale by getting Grandpa to hand over power of attorney, and she lures him into a trap while Austin Bucks offers Jake a final week to locate Grandma before the deal goes through. Desperate, Jake reaches out to the North Pole and is soon joined by Santa’s head elf, [Quincy], who explains that Santa took Grandma to the North Pole for medical care, but the accident had triggered amnesia and erased most of her memories. With this new understanding, Santa, Quincy, and Grandma resolve to head to Cityville to derail the contested deal.
But upon their arrival, Mel and her attorney, I.M. Slime, derail the plan by coaxing Grandma to accompany them away from the truth. Santa lays out the situation for Austin Bucks, and Jake and Quincy soon discover that Grandma has disappeared again. A showdown unfolds in which Mel accuses Santa of kidnapping and sets in motion a legal trap built on the fantasy of a miracle-rich Christmas fund, betting that a limitless fortune could silence the family’s concerns.
Three months later, Daphne Spankenheimer starts to suspect Mel’s involvement in Grandma’s second disappearance. Tracking clues to a secluded cabin in the woods, Jake and Quincy find Grandma being kept out of sight by Mel and I.M. Slime. They rescue her and uncover Santa’s letter detailing what happened and the true extent of Mel’s schemes, including the so-called reindeer-nip that made the reindeer act irrationally. Feeding Grandma some of her own fruitcake helps restore her memory, and they race to the courthouse to set the record straight.
Confronted with the evidence, Mel and Slime are arrested for obstructing justice and for nearly ruining Christmas, while the judge clears Santa of any wrongdoing. Realizing how deeply the family’s care for one another runs, Austin offers to franchise Grandma’s store nationwide, recognizing the value of a community-focused business. In a final, light-hearted twist, Grandma’s accidental exposure of Mel’s fruitcake—this time to the reindeer—gets Mel run over by a reindeer once again, a mishap that Jake and the grandfather rush to help them recover from, underscoring the story’s message that some things, like family and the holiday spirit, are irreplaceable.
