Harry Dunning

 is the janitor at South Lisbon High School in Lisbon, Maine.

Biography
Harry Dunning was born in Holden, Kentucky to Frank and Doris Dunning. When he was a child, he was hurt badly when his father killed his mother and siblings in a drunken rage on October 31, 1960. Harry sustained injuries which left him mentally disabled. ("The Rabbit Hole")

In 2016, he is a student in Jake Epping's GED class, while working as a janitor at the school. ("The Rabbit Hole")

1960
When Jake Epping goes back in time to 1960, he also decides to try to make Harry's life better by stopping Frank from killing his family. Jake tries to get them out of town, but Frank discovers the ruse and stops them. That night, Jake goes to Harry's house, gets into a fight with Frank, garrotes and kills him. ("The Kill Floor")

2016
After saving John F. Kennedy's life in 1963, Jake returns to discover Lisbon in ruins, destroyed by a nuclear war forty years ago. He sees Harry, who brings Jake back to a dilapidated warehouse where he lives. In the years after the war, his mother died of disease and his siblings disappeared.

He remembers Jake and asks him why he saved his family. Jake says he wanted to make his life better, but Jake realizes that this new world is not better. ("The Day in Question")