At the end of the original IT movie, the Losers Club (Bill Denbrough (Jaeden Martell), Ben Hanscom (Jeremy Ray Taylor), Beverly Marsh (Sophia Lillis), Richie Tozier (Finn Wolfhard), Mike Hanlon (Chosen Jacobs), Eddie Kaspbrak (Jack Dylan Grazer), and Stanley Uris (Wyatt Oleff)) believe they have defeated the evil clown Pennywise (Bill Skarsgård). In It: Chapter Two, we learn they only wounded Pennywise. He makes a violent return 27 years later to the town of Derry, Maine.
It: Chapter Two reunites the Losers Club 27 years to Derry. Mike had stayed in Derry to keep watch over the town. He knew he had to watch for Pennywise’s return. He was wise to do so.
When Pennywise returned, Mike (Isaiah Mustafa) began to call the old Losers (Bev (Jessica Chastain), Bill (James McAvoy), Richie (Bill Hader), Eddie (James Ransone), and Stanley (Andy Bean). He knew they had to make good on their commitment to return to Derry if ever Pennywise returned.