"Saw IV" is slashing the box office competition in North America. The horror sequel hooked audiences last weekend, taking in $32.1 million (USD) at the box office. Like the other "Saw" films, "Saw IV" revolves around a serial killer named Jigsaw, played by Tobin Bell. The film's big draw - the gruesome methods the killer uses on his victims - are often drawn out, messy and creative. Variety's Assistant Managing editor Dade Hayes, says the "Saw" film series "really introduced what people sort of derisively call torture porn to the landscape. It's basically this ultra intense focus on body parts and on mutilation and on the really gory, gory stuff. " "Saw IV" joins a rogues gallery of more than 40 horror movies released this year including the Quentin Tarentino-produced sequel "Hostel 2" and "Vacancy." But horror does not always equal a hit. In fact some recent splatter flicks have fallen flat. But, Hayes said, for the most part, horror flicks are a money-maker: "It's a very lucrative machine. It's almost engineered to be this renewable resource. If you look back over Hollywood history it has kind waxed and waned, but it's been a real mainstay of what the movie business is all about." While the audience is relatively small, as box office numbers showed last week, these movie goers are a loyal bunch that will follow the story into other media, from DVD's to Internet sites and film merchandise. So as the "Saw" franchise shows, horror movies that cut it with viewers are rarely one hit wonder.