“Sometimes I am two people,” the beloved country singer Johnny Cash once said. “Johnny is the nice one. Cash causes all the trouble. They fight.” This documentary tells the nice story—Johnny’s story—shedding light on the little known tale of his 13-year marriage with Vivian Liberto, who was 17 when they met (he was 18). Never-before-seen clips depict a father at home hosting birthday parties for his daughters, telling them bedtime stories. These were the early days, but the pressures of stardom were already coming for Cash. —E.C.