As the detention of migrant children has climbed to record-breaking levels under President Trump, FRONTLINE and The Associated Press investigate what's going on inside federally-funded shelters — and the lasting impact on children held in U.S. custody. During this two-part hour, in Iraq's Secret Sex Trade, BBC News Arabic's Nawal al-Maghafi reports from inside Iraq, where she investigates how some clerics are abusing an ancient Islamic marriage practice for the sexual exploitation of women and girls.