In Hollywood, when the cameras stop rolling, some stars go home to their husbands, wives and children. Others take a detour to invite-only parties where anything goes, including group sex, S&M, drugs, hookers, and every kind of debauchery. Welcome to the secret sex societies of the entertainment industry. E! News explores the underground phenomenon in a new series of two-hour specials, "Secret Societies of Hollywood," premiering on Thursday. "Within these exclusive members-only organizations, the search for excess can be found everywhere," the network claims. "From notorious Hollywood madams like Heidi Fleiss, who was believed to have supplied prostitutes for many big name stars, to an underground society of people who celebrate their love of bondage and other bizarre sexual tastes at parties that rotate from clubs and mansions to all over the city." FOX411 talked to one of the Hollywood insiders interviewed on "Secret Societies," who said the modern proliferation of paparazzi and tabloid journalism has forced more and more stars -- gay and straight, young and old -- to pursue their sordid interests behind closed, very high, very thick, doors. "Law enforcement stays away as they have no right to do anything regarding a house party, and there is usual careful discretion with these types of parties to make sure that there is nothing that could warrant unwanted attention," said alternative sentencing expert Wendy Feldman.