Johnny Cash at Folsom Prison.

Cash's concert at Folsom State Prison in California in January 1968 touched a raw nerve in the American psyche and made him a national hero at a troubled time in American history. Using the stark images of rock photographer Jim Marshall, graphic techniques, archive footage and interviews with Merle Haggard, Cash's daughter Rosanne, band members Marshall Grant and WS 'Fluke' Holland, alongside former inmates of the prison, the film documents this explosive concert, the live album that followed and a transformative moment in the lives of Cash, the inmates of Folsom Prison and the American nation in the troubled year of 1968.