The new documentary 13th, from acclaimed filmmaker Ava DuVernay (Selma), examines the rise of the corrupt prison system in the U.S. It argues that widespread abuse of inmates by guards, as well as the disproportionate persecution of young black Americans, originated from the least likely of places—the 13th Amendment to the U.S. Constitution, which abolished slavery.

Confused? Here’s the deal (and fair warning, it’s pretty horrifying): The 13th Amendment contains a loophole that allows for law enforcement to abuse and impose inhuman conditions on people who have been convicted. In effect, many inmates currently serving time are treated like animals. They are America’s modern day slaves. And as Senator Cory Booker points out in the film’s trailer, there are now more African Americans under criminal supervision in the U.S. than there were slaves in the 1850s. Chew on that for a moment.

13th presents a riveting and informative look at the catastrophic legacy of the 13th Amendment and the rise of the vast (and lucrative) incarceration system in the U.S. You can watch the trailer above, and stream 13th only on Netflix.