Legal clerk Ray Ellison, living in Memphis, goes to see Dr. Tate and is informed that he has a lethal brain tumor. The doctor knows a specialist but warns that the treatment is expensive. Ray admits he has no money, no family, and no friends. Depressed at the fact he isn't leaving anything behind, Ray leaves and while walking across the street, is hit by a car. He wakes up to find himself surrounded by African-Americans wearing antiquated clothing. A nurse, Adelaide Tyler, checks his condition and reveals that somehow Ray has been transported to Memphis... in 1968.
Adelaide and her son Lucas take Ray home to let him recover. Ray intrigues Lucas, who has a large birthmark on the left side of his face. Adelaide talks to Ray and warns that only a colored hospital will see him, and all he needs is rest. Ray wonders if he's hallucinating and notices that his wallet is missing. That night, they have supper but during a private moment with Lucas, the boy tells Ray that Adelaide is worried because they received a foreclosure notice on their home. Ray finds the letter from the company and later takes it to Adelaide. She's angry that he's been poking into her affairs but he says that he can help her.
The next day, Adelaide goes to the foreclosure hearing while Ray goes to find his wallet. Lucas wonders if he's coming back and ray admits that he probably isn't. Ray goes to the alleyway, unconsciously taking a flyer from a black man. As Ray looks through the garbage for his wallet, a police officer demands to know what he's doing and asks to see his ID. When Ray insists he doesn't have any because he lost his wallet, the officer moves in but Lucas arrives to vouch for Ray. The officer knows Lucas and lets the matter slide.
As they go home, Ray wonders why Lucas is home on a school day. Lucas explains that he got into a fight with a kid who was taunting him because of his birthmark, and got sent home. Ray says that it's important to fight with the heart and the mind, not just fists, so you can change the future. Lucas whispers to Ray what he plans to do with his future and Ray admits it's a pretty major plan. They arrive home and Adelaide tells Ray that his advice was a success: she stopped the foreclosure. Later when Lucas is in bed, Adelaide explains that her husband died in an accident when nobody would take him to the colored hospital. Ray says that things will change but then notices the flyer in his pocket. It advertises Reverend Martin Luther King Jr. giving a speech that night: the eve of King's assassination on April 3.
Believing that's why he has traveled back through time, Ray tries to go to the speech to warn King but the police haul him away. Adelaide bails him out the next day and Ray runs to the Lorraine Hotel where King was shot. Lucas follows on his bike and Ray gets to the hotel. He sees a car approaching Lucas and has to choose; he steps in front of the car to stop it before it hits the boy. As he lies on the ground, he hears a gunshot. Lucas thanks Ray as he starts to fade into unconsciousness.
Ray wakes up in the hospital where Dr. Tate informs him that he underwent the surgery: the specialist runs a special program for the needy. Ray is introduced to the new specialist: Dr. Lucas Tyler. Dr. Tyler has the same birthmark on his face and says the same thing about fighting with the heart and the mind. Ray realizes that he has made a difference, and promises that he'll never forget.