parlors, ed walsh has a unique window on the sordid business of human trafficking. >> hi, health department. how are you? >> hello, ladies. >> every day he comes face to face with dozens of immigrant women from all across asia. >> i made it to see your i.d.s. >> many, he suspects, are indentured servants in the underground sex trade. afraid to talk or reveal they're not free to leave the premises. >> getting a lot of customers here? no customers. >> today he is quick to notice telltale signs that often distinguish legitimate massage parlors from houses of prostitution. >> there's a lot of signs. typically you can look from the outside of the facility. there will be double doors or locked gates. there will be cameras on the outside of the facility so they can view the whole sidewalk. >> hi, health department. how's everybody? you walk into the facility, you'll find girls that are improperly dressed. you will find high heels,