Cobb led off the evening by showing samples of her blockbuster Geographic story about the global trade in slaves. Yes, she assured the crowd, slavery exists and is growing. “It’s the third largest criminal enterprise in the world,” she noted. Her images—young girls in Africa being sold into marriages with older men, European women forced into prostitution in Israel, children and adults alike working in bondage in brick kilns in India (above)—take the masterful aesthetics of National Geographic photography into a new area. “Essentially, these pictures are evidence,” Cobb said. And powerful evidence, at that: The story, said Cobb, provoked the biggest reaction from readers in the history of the magazine.