Between 2009 and 2011, Shane Bauer spent nearly two years locked up in an Iranian prison as one of the jailed American hikers. Last year, he went back to jail—this time as an undercover journalist working as a guard at a private prison in Louisiana. In a stunning new exposé for Mother Jones, Bauer chronicles the four months he spent undercover last year as a guard at Louisiana’s Winn Correctional Facility. Winn is the oldest privately operated medium-security prison in the country and sits in the state that holds the distinction as having the world’s highest incarceration rate—more than 800 prisoners per 100,000 residents. During Bauer’s investigation, Winn was run by the Corrections Corporation of America, the nation’s second-largest private prison operator. Bauer’s story offers a never-before-seen look at the for-profit prison industry, exposing conditions that include violence among inmates, poor medical and mental healthcare for even the sickest prisoners, mismanagement and lack of training for staff.