Jake Epping
Jake Epping is the protagonist of the novel. A high school English teacher, Epping lives in Lisbon Falls with his wife. However, toward the start of the novel, it is revealed that the two are getting a divorce, something that understandably devastates Jake. He is a kind, intelligent, and reasoned man, but his life has been missing a piece for a while. He looks for meaning everywhere and finds it one late night while talking with his friend Al in Al's diner.
While talking with Al, Jake is introduced to a time portal. Al tells Jake about his lifelong dream to travel back in time to stop President John F. Kennedy's assassination (his portal allows travel back to 1958, 5 years before the assassination). Al believes that preventing Kennedy's assassination would have positive effects on history and would have stopped the Vietnam War. Thus far, Al has never been able to move forward with his plan and feels that he will never be able to complete the plan due to his terminal cancer—terminal cancer which shockingly developed overnight. Al asks Jake if he will complete his mission, and Jake agrees.
Despite the physical and personal challenges that Jake experiences throughout the novel, he is steadfast in his commitment to completing his mission. However, Jake also experiences the challenges and dangers associated with meddling with time. Likewise, he finds true love in an unexpected place: in the past.
Al Templeton
Al is the owner of a retro diner in Lisbon Falls, Maine. The diner has become a hotspot for the town's residents who seek refuge from the tumult of everyday life. The diner has a massive secret: it has a time portal in its pantry, which allows users to travel back to 1958. Al has developed a fascination with traveling back in time to prevent JFK's assassination so that the Vietnam War wouldn't happen. However, Al’s failing health (he contracts terminal cancer overnight) prevents him from completing the mission himself; he asks Jake to take up the torch for him. Jake agrees.
Sadie Dunhill
Sadie is a librarian in Sadie, Texas, where Jake lives, while preparing to stop Lee Harvey Oswald on a fateful day. When Jake first traveled back in time, his heart was open to the potential of finding love. But he never expected to find it until he meets Sadie, who is intelligent, strong, and compassionate—qualities which Jake is instantly attracted to. She becomes an integral part of Jake's mission to save John F. Kennedy, accompanying him on several missions.
Bill Turcotte
Bill Turcotte becomes fast friends with Jake Epping and eventually helps Jake on his mission to save John F. Kennedy from assassination. The two meet when Jake saves Bill, who is being attacked by his violent and abusive stepfather in a small town in Maine. He becomes Jake's partner in his quest to stop the assassination and assists Jake in surveillance and investigation efforts.