Jake Epping is a high school history teacher who learns from his father about the existence of a portal in time, in a closet. His father gives him the mission to return to the past to prevent the assassination of US President John F. Kennedy. The dangers that Epping will face when accepting this task are the confrontation of Lee Harvey Oswald, the one accused of shooting J.F.K., a beautiful woman who makes him fall in love and the past itself, which does not want to be changed.