It In the month of October twelve-year-old Bill Denbrough builds a sailboat out of paper that carries Georgie. Georgie is sailing the boat through the rainy streets of small town Derry, Maine but it is then able to fall down a storm drain. While trying to retrieve it, Georgie sees a clown in the drain, whom he introduces as ” Pennywise the Dancing Clown”. Pennywise seduces Georgie and drags her down the drain.
The following summer in June 1989, Bill and his friends Richie Tozier, Eddie Kaspbrak and Stan Uris run afoul of older bullies Henry Bowers, Belch Huggins, Patrick Hockstetter, and Victor Criss. Bill, still troubled by the disappearance of Georgie believes that his brother’s remains might have washed up on the marshy desert called the Barrens. Since he believes Georgie is alive, he asks his friends to assist him. Ben Hanscom, one of Bill’s new friends, discovers that mysterious tragedies and child disappearances have plagued the town for centuries. Targeted by Bowers group, Ben flees into the Barrens and joins Bill’s class. They track down the woman who was missing identified as Betty Ripsom, while Patrick is murdered by Pennywise while searching in the sewers to find Ben.
Beverly Marsh is one of the girls who is bullied for her rumored prostitution. Both Bill and Ben form feelings towards her. In the following days, the group meets orphan Mike Hanlon after rescuing him from Bowers. The group has encountered frightening manifestations of the terrifying clown that attacked Georgie: a headless undead boy (Ben), the sink that spews blood only children can see (Beverly) as well as a diseased and rotting leper (Eddie) A threatening painting that has come to life (Stan), Mike’s parents burning alive (Mike) as well as the frightening phantom of Georgie (Bill). Now calling themselves “The Losers Club”, they realize they are all being stalked by the same entity, which they refer to as “It”. They realize that it is their greatest fear, awakening each 27 years to feast on the children of Derry. After that It moves about using the sewer lines which lead to an old stone well beneath an abandoned home on Neibolt Street. After Pennywise attacks the group, they go into the house to take on It but are divided and frightened. As Pennywise boasts at Bill about Georgie’s, Losers gather and Beverly impales Pennywise through his head, forcing him to retreat. The group leaves the house, and it starts to split, with Bill and Beverly being the only ones who are determined to fight It.
A few weeks later, when Beverly confronts and suffocates her abusive sexual father, Pennywise abducts her. The Losers Club reassembles, and returns to the home to rescue her. Bowers who killed his abusive father following being demented by It, attacks the group; Mike fights back and pushes Bowers down the well. The Losers plunge into the sewers and find the underground cave, that is filled with decomposing circus props and child’s toys, on which the corpses of It’s children’s victims are floating in mid-air. Beverly is now in an euphoric state, having been exposed to the bright light of It’s mouth. Ben then kisses her to bring her back to consciousness. Bill is able to meet Georgie, but recognizes that he’s It in disguise. It holds Bill hostage as Pennywise and offers to rescue the others however it’s going to go into hibernation If Bill lets It eat on his body. The losers reject the offer and fight It, while overcoming different fears. It retreats further into the sewers and is defeated. Bill declares that it will be starving in its hibernation. After discovering the remnants of Georgie’s raincoat, Bill is finally able to come to terms with his brother’s death while his friends comfort the grieving man.
As summer ends, Beverly informs the group of a vision she experienced while catatonic, where she was able to see them fighting It again , this time as adults. The Losers swear to a blood oath that they will be back in Derry as adults in the event that It returns. After everyone says their final goodbyes and leave, Beverly and Bill discuss her leaving the following day to stay with her aunt in Portland. Bill shares his feelings with Beverly, and they share one last kiss before she leaves.