After nearly three decades of being Santa Claus, Scott Calvin’s magic begins to falter. As he struggles to keep up with the demands of the job, he discovers a new clause that forces him to rethink his role as Santa and as a father.

In 1962, amid a spate of unexplained disappearances of local children, a group of misfit friends begin to suspect a long-buried ancient evil lurking. As the kids set out to determine what's really going on, a rising unease prompts several townspeople to work together to restore peace – all while a U.S. military operation seeks to exploit Derry for its own objectives.