Shady massage parlors and "spas" that offer sex -- commonly referred to as a "happy ending" -- after your back rub highlight a serious and often overlooked issue -- human trafficking of sex slaves. Store fronts that peddle prostitution may seem innocent enough -- even though they are illegal-- with ads on sites like Backpage.com featuring scantily clad women, who are usually Asian, posing for provocative photos alongside captions that "promise a good time."