NEW YORK (Reuters) - On a recent October night, Ruben Perez's friends set out to show him the worst that New York City has to offer.
"I got kidnapped," said Perez, 35, a psychologist. "Naturally you get shocked, so your heart starts pumping."
Among the evening's highlights were encounters with mole people - mythical mutants born in the subways - and a run-in with a sewer alligator. All were part of the Halloween scene at Nightmare New York, a haunted house for adults.
With Hollywood-grade stagecraft and professional actors, haunted houses are in increasingly high demand. One in five Halloween celebrants over the age of 18 plans to visit one this year, up from one in six in 2005, National Retail Federation figures show. There are about 2,000 haunted houses charging admission in the United States, according to HauntWorld magazine.
Nightmare welcomes about 35,000 annual visitors, each of whom pays up to $60 to take part in scenes from New York's darkest days, featuring characters, real or imaginary, from outsize rats said to be spawned by Hurricane Sandy to the 1970s serial killer David Berkowitz, better known as the Son of Sam.
Behind-the-scenes control systems cue lighting, sound and animatronics through pressure plates and motion sensors, said David Hinkle, Nightmare's production designer.
At a recent performance, a raggedy wide-eyed man shouted: "Get out of here. I was eating rat!" sending two female visitors into a frenzy.
Patrons who choose the "extra-crispy experience" paint a fake-blood cross on their foreheads, giving permission to the show's more than 35 actors to break the customary no-touching rule.
Some haunted houses have ditched all reference to Halloween superstitions to focus solely on scares inspired by real-life occurrences.
Blackout Haunted House, with locations in Los Angeles and New York, is among the pioneers of this breed, with performances featuring profanity, intimidation and sexually-charged scenarios to send extra-realistic shivers down a visitor's spine.
Guests, who must be over age 18, are given a safe word before entering, should they want to call off the experience in progress.
"Nothing that we do is really overtly Halloweenie," said co-creator Josh Randall.
"While I don't want people coming in expecting a recreation of an Abu Ghraib torture scene, because that's not what we're doing, a lot of the tactics we do use could fall under that category. But there's nothing so blatantly obvious as to say this is a torture scene," he said.
The attraction, in its sixth season, so far has drawn an estimated 20,000 guests.
But not everyone is pleased with the direction the haunted house market is taking. Some business leaders say that experimentation with extreme concepts risks smearing the entire industry.
They point to last year's Naked and Scared Challenge, a haunted house experience that invited visitors to face their fear of nudity by stripping down to lower-body undergarments.
In Tennessee, Frightmare Manor has outraged some by featuring murder scenes based on 19th Century serial killer Jeremiah Lexer at his actual former plantation.
And near Chicago, a room in heavy metal musician Rob Zombie's Great American Nightmare dedicated to 1970s local serial killer John Wayne Gacy is drawing heavy criticism from the local community in Villa Park, Illinois.
Editing by Barbara Goldberg and Gunna Dickson