Al Templeton shows Jake a portal into the past, located in his pantry. Al is diagnosed with lung cancer and urges Jake to continue his work he has started, saving JFK.
When traveling through the portal into the past, Jake is met with the "yellow card man". Only the next time Jake travels through the portal, the card is orange, and the next time, black, and the man is dead. After Jake Saves JFK, he returns again finding a new green-card man.
Current Year: 1958
One of Jake's students, Harry, who is the school janitor, writes an essay about the day his father killed his brother, sister, and mother. When Jake goes into the past, he saves the family by killing Harry's father when he is visiting a grave.
Jake occupies several teaching positions before meeting a girl named Sadie, who he quickly got along with.
After getting out his hospitalization, Sadie helps Jake remember his goal, and helps him stop Lee Harvey Oswald from assassinating JFK. They are successful, although Sadie dies in the process
Jake travels back to the present, and finds the world a nuclear slump. He finds Harry Dunning, who explains what transpired. Jake goes back into the portal to revert his actions