J.R. Cash takes an early interest in music while growing up on an Arkansas cotton farm in the Great Depression. He is very close to his elder brother Jack, who dies in an accident involving a table saw in 1944 when J.R. is out fishing. His guilt about this event is not helped when his father blames him as well, so it comes as a welcome escape when he is old enough to enlist in the air force and is sent to Germany. Inspired by a film he sees there, Inside the Walls of Folsom Prison he composes a song, "Folsom Prison Blues." Leaving the air force Cash marries and attempts to succeed as a door-to-door salesman in Memphis, Tenn. but his heart is in music and he succeeds in an audition with Sam Phillips at Sun Records. Soon Johnny is touring and meets June Carter, who has been a country star since childhood.

Although they are drawn to each other, they are married to others. Touring takes a toll on Johnny's marriage, and in the 1960's he becomes addicted to amphetamines. His marriage ends and June helps him beat the drug dependency. Reading fan letters from prisoners inspires Cash to perform a concert at Folsom Prison, which leads to a very successful album. June finally accepts Johnny's proposal of marriage given as they perform together on stage in Ontario in February, 1968.