The exodus of North Korean defectors into China began in late 1990s after a severe famine that destroyed at least one million of its 23 million people. Once they cross the border to China, they'll be in hiding and waiting to embark on an extremely secretive, dangerous escape route, known as Asia's Underground Railroad from northern China all the way to Laos, crossing Mekong River, to Thailand and finally to South Korea.

The unpredictable journey can take weeks, months or even years. Chinese police routinely hunt for North Koreans attempting to escape cross-country. Police crackdowns can net hundreds of victims. If they are caught while escaping in China and Laos, they will be repatriated to totalitarian North Korea, facing severe labor camps or capital punishment. Magnum photographer Chien-Chi Chang traveled with the defectors to document the darkest journey in 2007 and 2008. To date, He has continued to document the plight of North Korean defectors.