Mike is hated by Henry Bowers. Henry picks on Mike every chance he gets and even poisoned his dog, Mr. Chips.
Mike encounters a giant, prehistoric-like bird when exploring the Kitchner Ironworks. He hides in a smokestack until the bird goes away. IT reveals that Mike is afraid of this form from a very early memory of a crow pecking him when he was only 6 months old.
Mike went to Neibolt Street Church School (on account of his mother being a devout Baptist). Mike is the last to join the Losers Club, bringing them to lucky number 7. While Henry and his friends are chasing Mike through the tiwn dump Henry throws an M-80 at him. The Losers Club comes to his rescue in what comes to be known as The Apocalyptic Rockfight. The Losers beat Henry's gang, and Mike becomes a member of their group.
Mike brings his father's photograph album to the barrens and shows the others that a clown appears in several pictures of Derry dating back as far as a hundred years.
When The Losers use their clubhouse to try an old Indian ritual to get a vision Mike and Richie see It landing on Earth from beyond space in a time long ago.
Mike is the only one of his friends to remain in Derry. He becomes the town librarian and intends to write a book on the history of the town. He's also the only one to remember the summer of 1958. He calls the other six when the murders begin again in 1985.
He nearly bleeds to death after Henry Bowers stabs him in the leg. He does not go into the sewer with the others because of his injuries. While in the hospital a nurse named Marc Lamonica tries to kill him but Mike is able to fight him off until the other nurses after hearing the commotion. He later recovers from his wounds, but, like the others, starts to lose his memory.
It Chapter One & It Chapter Two
Mike works on his Grandfather Leroy's farm, as his parents died in a fire when he was child. This is the main source of fear that It uses against him. He is also troubled by the town dismissing it as drug induced death and the legacy this leaves him with. He also has issues with slaughtering sheep on the farm. Before the rockfight, he is chased by the Bowers Gang as he does his meat delivery. In the barrens before the Losers arrive, he sees Pennywise waving Eddie Corcoran's arm at him. As the Losers arrive to help they become fast friends. He tells them how his grandfather believes the town is cursed and due to a couple of close calls with Pennywise, decides against fighting It and separates from his friends for a bit, feeling he would survive as an outsider. However, when Beverly is kidnapped, he unites with his friends to rescue her and supplies the bolt gun for the final confrontation with It. Mike has a glorious moment when he defeats Henry Bowers in a short scuffle, knocking him down the well. At some other point in time, Mike talks about getting out of Derry after graduation and going to Florida.
Mike is the only one to remain in Derry, and lives in the library as he collects information on It through town history and trying to find ways to defeat it. At some point in his adult life he meets a native American tribe who once fought It. He goes through the Ritual of Chüd and witnesses the arrival of It as well as seeing the Natives trap It before being killed. When he tells the Losers he knows how to defeat It, he doesn't share with them the Native peoples outcome, as he fears their knowing will lead them not to believe and the Ritual to not work.
He is attacked by Henry Bowers at the library but is not seriously injured. After defeating It, as the Losers all remember each other, he keeps in contact. Having spent his entire life in Derry and no longer having a reason to remain, Mike decides to leave the town and start a new life elsewhere, presumably Florida.
- 11/22/63 (mentioned)
- Dreamcatcher (mentioned)
- It: Chapter One (2017 film)
- It: Chapter Two (2019 film)
- "Thanks, Guys. But, you shouldn't have done that. He'll be after you too now."
- ―Mike to the Losers Club
- "Maybe. Or maybe IT knows what scares us most and that's what we see."
- ―Mike to the Losers' about IT knows about their fears
- "You know the that burnt down house on Harris Avenue? I was inside when it burned down. Before I was rescued, my mom and dad were trapped in the next room over from me. They were pushing and pounding on the door trying to get to me. But it was too hot. When firemen finally found them, the skin on their hands melted down to the bone. We're all afraid of something."
- ―Mike reveal his past about the Harris Avenue burnt down house and his parents' deaths
- Plays the trombone in The Church School Marching band on the 4th of July
- Chapter 21 "Under the City", section 3 "It/May 1985"