As the Whos’ in Whoville prepare for their cherished Christmas festivities, the Grinch, a grumpy green creature living in a cave on Mount Crumpit, can’t stand the holiday and plots to spoil it for everyone. Meanwhile, six-year-old Cindy Lou Who, feeling let down by the town’s focus on material gifts, unexpectedly meets the Grinch at the local post office. During this encounter, he saves her from a disaster with a mail-sorting machine, sparking her curiosity about his dislike for Christmas.
Intrigued by the Grinch’s disdain for the holiday, Cindy discovers from the townsfolk that he was left alone as a baby and later taken in by two elderly sisters in Whoville. In school, the Grinch had a crush on a girl named Martha May Whovier, who liked him back. However, Augustus May Who, who was envious of their connection, often bullied the Grinch for his unusual looks. To impress Martha, the Grinch attempted to shave but injured himself. After being mocked by Augustus and his classmates during a Christmas event, he lost his temper and declared his hatred for the holiday, feeling ashamed and retreating to Mount Crumpit, promising never to return.
Cindy decides to include the Grinch in the Christmas celebrations by nominating him as the town’s Holiday Cheermeister, which frustrates May Who, the current mayor. Although hesitant, the Grinch sees this as a chance to face his childhood bully and possibly reconnect with Martha, who now lives next to Cindy. During the festivities, the Grinch tries to join in on the fun, but his enjoyment quickly fades when May Who gives him an electric razor, reminding him of his painful past. To make matters worse, May Who publicly proposes to Martha, presenting her with a new car as a gift. Enraged, the Grinch lashes out at the Whos, accusing them of being obsessed with materialism, and in a fit of anger, he shaves the mayor’s head, sets the town’s Christmas tree ablaze, and goes on a wild rampage before retreating to his cave on Mount Crumpit.
After witnessing the Whos’ determination to celebrate Christmas despite their losses, the Grinch devises a plan to steal all their holiday cheer while they sleep. He disguises himself as Santa Claus, dresses his dog Max as a reindeer, and then descends into Whoville on a high-tech sleigh. His first stop is Cindy Lou Who’s house, where he gets caught stealing their Christmas tree. Quick on his feet, he lies to her, claiming he is Santa taking the tree for repairs, and manages to escape. With a methodical approach, he empties the entire town of its Christmas decorations, gifts, and food, stuffing everything into a massive sack before hauling it up to Mount Crumpit, where he plans to dispose of it all.
On Christmas morning, the Whos wake up to find that their holiday has been ruined by the theft, leaving the entire town in shock. Mayor May Who blames Cindy for letting the Grinch spoil their celebration, but her father, postmaster Lou Lou, stands up for her. He reminds everyone that the essence of Christmas goes beyond just presents and decorations. Motivated by his words, the Whos unite, hold hands, and start singing Christmas carols, proving that their holiday spirit is still alive and well.
As the Grinch is about to dump the huge sack off the mountain, he hears the Whos singing joyfully below and realizes his plan has backfired. Touched by the true spirit of Christmas, the Grinch feels his heart expand with warmth and emotion. Just then, the sleigh, with Cindy Lou Who on board, starts to slide off the cliff. In a brave act, the Grinch saves both Cindy and the sleigh, returning all the stolen Christmas items to the Whos. Back in Whoville, the Grinch apologizes and turns himself in, but the authorities decide to forgive him despite Mayor May Who’s insistence on punishment. Tired of May Who’s selfishness, Martha May returns his engagement ring and declares her love for the Grinch. Ultimately, the transformed Grinch invites the Whos to celebrate Christmas in his cave, where he carves the Roast Beast at the feast, finally accepted as part of the Whoville family.
