The world knows about China’s one-child policy, its deceptively simple drive from 1979 to 2015 to stave off what was widely accepted as a population crisis.

But director Nanfu Wang, now an American citizen and new mother, travels back to her home country to dig into the uncomfortable—no, harrowing—details of what that edict actually meant, starting with her own family and village in Jiangxi province.

The personal quest begins with interviews with her mother, who contemplated abandonment, and an aunt whose female newborn was left out in a basket to die of exposure. It leads to interviews with the town administrator who dragged women to sterilizations and demolished the homes of those who broke the rules, and to the midwife-nurses who were celebrated as heroes by the People’s Party after helping with thousands of forced full-term abortions.

The road winds further, into the propaganda posters and folk arts used to enforce the one-child message, to even wider blame: sinister proof that China’s nationally owned orphanages were buying abandoned and state-seized babies to feed a lucrative western-adoption market. Along the way, Wang and codirector Jialing Zhang expose the human suffering paid for what was a questionable experiment in the first place. In bold and damning terms, they’ve created a shocking portrait of the power of mass indoctrination—and the kind of collective amnesia that can set in in just four short years.