The novel is the story of seven friends from the fictional town of Derry, Maine, and is told with the narrative alternating between two different time periods. In the late 1950s, when they are twelve years old, the seven discover the existence of a shape-changing monster (which they call "It") and try to kill it. They make a pact to return and fight It again if It returns. All but one of them move away from Derry and begin to forget about the events, but one of them, Mike, remains and calls them back when It begins to kill again. In the 1980s, the friends return to finish killing the monster.