It may seem obvious that a show about preventing the assassination of John F. Kennedy would come with an adversary in Lee Harvey Oswald, but the real foe in Hulu’s “11.22.63” is time itself — specially, changing it.

“The key, core rule of this world that Stephen King created is that the past doesn’t want to be changed. So you feel it. You feel events, the past and the world doesn’t like it when you try to change things. It is in fact dangerous,” showrunner Bridget Carpenter told Variety in a recent interview, ahead of the show’s launch.

In the adaptation of King’s novel, Jake Epping (James Franco) is tasked with traveling back to the ’60s and stopping the assassination of JFK. The man-out-of-time finds that knowing your facts and being in the right spot at the right time isn’t going to cut it. Changing the past has consequences.

“They’re near fatal,” Carpenter said. They’re as bad as it can be. It’s also kind of commensurate to the change. You can walk down the street and buy a root beer and the past is going to go, ‘Eh, OK.’ But when you try to do things that are more major, that affect people’s lives, that affect whether people live or die, that’s when it gets hairy. Big consequences.”

In the series’ premiere episode, which debuted last week on President’s Day, Chris Cooper’s character Al gave Jake the mission to travel back in time and change the course of the past because he thinks JFK’s death was the first domino to fall that led to events like his brother Robert Kennedy’s assassination and, more importantly to him, the Vietnam War.

That very thought of singular moments in time sparking worldwide changes was what drew Carpenter to the story.

“It raises the hair on my arms even now, but he’s kind of going, ‘Look, one death can save thousands, maybe millions.’ I love that idea that one single act can have something that’s very deep and consequential,” she said.

But beware: The remainder of the series will have its fair share of fallout from Franco’s character altering history. As Al (Cooper) said in the first episode, “The past doesn’t want to be changed. If you do something that really f—s with the past, the past f—s with you.”

Reporting by Elizabeth Wagmeister.