Thousands of years after civilization was destroyed by a cataclysmic event, humankind has adapted and a new way of living has evolved. Gigantic moving cities now roam the Earth, ruthlessly preying upon smaller traction towns. Tom Natsworthy (Robert Sheehan)—who hails from a Lower Tier of the great traction city of London—finds himself fighting for his own survival after he encounters the dangerous fugitive Hester Shaw (Hera Hilmar). Two opposites, whose paths should never have crossed, forge an unlikely alliance that is destined to change the course of the future.

Each year at Christmas they disrupt his tranquil solitude with their increasingly bigger, brighter and louder celebrations. When the Whos declare they are going to make Christmas three times bigger this year, the Grinch realizes there is only one way for him to gain some peace and quiet: he must steal Christmas. To do so, he decides he will pose as Santa Claus on Christmas Eve, even going so far as to trap a lackadaisical misfit reindeer to pull his sleigh.

Meanwhile, down in Who-ville, Cindy-Lou Who—a young girl overflowing with holiday cheer—plots with her gang of friends to trap Santa Claus as he makes his Christmas Eve rounds so that she can thank him for help for her overworked single mother. As Christmas approaches, however, her good-natured scheme threatens to collide with the Grinch’s more nefarious one. Will Cindy-Lou achieve her goal of finally meeting Santa Claus? Will the Grinch succeed in silencing the Whos’ holiday cheer once and for all?