In October 1988, Bill Denbrough gives his six-year-old brother, Georgie, a paper sailboat. Georgie sails the boat along the rainy streets of small town Derry, and is disappointed when it falls down a storm drain. As he attempts to retrieve it, Georgie sees a clown in the sewer, who introduces himself as Pennywise.
The clown entices Georgie to come closer, then severs his arm and drags him into the sewer. The following summer, Bill and his friends – Richie Tozier, Eddie Kaspbrak, and Stan Uris – run afoul of older bully Henry Bowers and his gang. Bill, still haunted by Georgie’s disappearance and the resulting neglect from his grief-stricken parents, discovers that his brother’s body may have washed up in a marshy wasteland called the Barrens.
He recruits his friends to investigate, believing his brother may still be alive. Ben Hanscom learns that the town has been plagued by unexplained tragedies and child disappearances for centuries. He is targeted by Bowers’ gang, after which he flees into the Barrens and meets Bill’s group. They find the sneaker of a missing girl, while a member of the pursuing Bowers Gang, Patrick Hockstetter, is killed by Pennywise while searching the sewers for Ben..