In October 2011 in the tiny town of Le Roy, New York, a handful of teenage girls from the same high school suddenly developed symptoms that looked like Tourette's syndrome: facial twitching, violent limb gestures and uncontrollable verbal outbursts.
Some doctors believed they were victims of conversion disorder, where real physical symptoms - in this case tics - are triggered not by a physical cause, but by psychological trauma. But within a few months 18 students were sick and the diagnosis became 'mass hysteria'.
As a cry for help, the girls went on national TV and their story caused a global media frenzy.
This remarkable documentary meets the people at the heart of this outbreak, including the girls who have recovered, as well as those who are still suffering.