 Seven-year-old Sarah was one of five people to die in a dangerously overcrowded boat off a beach in northern France. To track down the smuggler who'd organized her family's trip, one of our team posed as a migrant. On a phone call, the smuggler, an Iraqi called Rebwa Zangana, confirmed he was still in business. We then tracked him from France to Belgium to Luxembourg, where we confronted him on the street. He denied any involvement.