(CNN) -- Zak Bagans tiptoes into a darkened bedroom, hunting a predator.
"Are you here, can you talk to us?" he asks, scanning the empty room where he just heard mysterious steps.
Bagans was summoned to Victoria's Black Swan Inn in San Antonio because something strange was afoot. Jo Ann Rivera, the inn's owner, told him that disembodied voices threatened to kill her, invisible hands groped her, and something yanked the sheets off her daughter's bed at night, leaving bruises on the girl's legs.
Bagans, the buff star of the Travel Channel's "Ghost Adventures" series, is prepared to do battle, but with what he does not know. As he and Rivera creep through the darkness, they are about to find out.
"Something just came up on me and backed me up," Bagans says, his voice rising in alarm.
Rivera turns to respond, and her eyes widen in shock.
They have a "visitor."
Chasing gigs instead of ghosts
We've heard of ghosts that harass the living. Now people are starting to harass the ghosts. Virtually every night on television, a paranormal investigator like Bagans can be seen trying to summon a ghost or "dark spirit." All across America, novice investigative teams are creeping through people's homes at night, trying to get rid of their paranormal pests.
The public's fascination with the paranormal, though, has created a problem. Ghost-hunting teams are chasing television gigs more than ghosts, some investigators say. The allure of fame, they say, has done what the forces of darkness could not do -- turn ghost hunters against one another.
The stars of some paranormal shows feud over whose show is real or fake. Local ghost-hunting teams refuse to work together because they see each other as business rivals. Some teams refuse to share spooky "evidence" captured on film because they plan to use it as a demo tape for a potential television pilot or a Hollywood movie like "The Conjuring," investigators say.
For years the paranormal community functioned like an extended family: People bonded over shared experiences with the supernatural and joined one another on ghost-hunting expeditions. Now, though, the feuding has turned so toxic that some ghost-hunting groups have mounted a "Paranormal Unity" campaign via social media to get rid of all the "paradrama."
"With all of these paranormal shows, we're asking people to unite and to quit being so selfish and childish and share evidence and experiences with one another," Bagans says. "People don't need to compete against one another."
That may be unavoidable, though, because the law of supply and demand is hitting the paranormal community. There's a ghost-hunting glut: too many teams and not enough hauntings to go around, says Bill Wilkens, who created paranormalsocieties.com, a national online database of ghost-hunting teams across the United States.
Wilkens says 4,413 ghost-hunting teams are registered on his site, and 200 more have asked to be added. His site also lists potential cases. Movie producers and casting directors frequently call him, asking for the creepiest stories and the most telegenic investigators. He had to hire an assistant to help him run the site.
Everybody, it seems, wants a piece of that paranormal pie.
"Sometimes when I post a case," he says, "I might have eight teams respond."
Why ghost hunters are sexy
Paranormal investigators used to be as coy as the ghosts they tried to coax into the open. Many hid their vocation from neighbors and friends because they didn't want to be called kooky. Now they're cool. They speak at corporate events, land book deals and get appearance fees at college lectures and paranormal conferences.
Ghost hunters have gone from being nerds to action stars. Some have even become sex symbols.
"It's true," says Steven LaChance, a paranormal investigator who wrote "The Uninvited." The 2008 book is a harrowing account of what happened to his family when they moved into an old home he says was haunted by malevolent spirits.
When "The Uninvited" was featured in a Discovery Channel documentary, LaChance says he was contacted by women who thought there was something hot about a man tangling with the supernatural.
LaChance chuckles at his new image. He mimics the voice-of-doom baritone of a horror movie narrator:
"He was the guy who fought the devil for his children. He stood toe to toe with the devil."
Click onto some paranormal stars' websites and you'll see men dressed in tight black T-shirts, black shades and leather jackets, staring into the camera with grim determination. Most of these stars may be men, but the fan base is primarily women.
Bagans, host of "Ghost Adventures," embodies the new ghost-hunter-with-an-attitude persona. He often taunts ghosts during his investigations ("You want us; you got us"), and one of his most memorable scenes came when he took off his shirt during an investigation, revealing his muscles and tattoos.
"There're definitely girls into that," says Wilkens, of paranormalsocieties.com. "It's a bad-boy thing."
Bagans has become a brand. On his website, he cradles a silver skull while advertising his Twitter handle. He has his own "Dungeon Wear" clothing line and a "NecroFusion" rock album for sale, and he has posted an interview with Muscle & Fitness magazine to share the secrets of his chest workout.
He says he's been criticized by investigators on another popular paranormal television show, but he won't say who.
"It's unfortunate that some shows feel like they own the paranormal," he says. "There's one show in particular, they talk a lot of crap."
Before paranormal investigators fought one another, though, they first fought for credibility.
Critics have long said ghosts don't exist and that paranormal shows are faked. Even "South Park" lampooned the overactive imaginations of ghost-hunting teams by depicting one duo as flinching at every stir of the wind before asking, "Did you hear that?"
One of the most formidable critics of the paranormal community is a former detective and magician who says he knows all the tricks.
Joe Nickell has been investigating hauntings since attending his first séance in 1969. He has been featured on many television shows debunking the supernatural, and has written a book aimed at disproving some of the most famous paranormal cases, "Entities: Angels, Spirits, Demons and other Alien Beings."
Nickell says he's never seen a ghost or any other supernatural entity in 44 years of investigations.
"I've never been able to find one," he says.
He has a theory, though, about why people are so fascinated with the paranormal.
"The paranormal, by and large, promises pretty wonderful things," he says. "If ghosts are real, then we don't really die. If I were voting, I would vote for that. There's a big market for this."
The show that started it all
The market for the contemporary fascination with ghost hunters can be traced primarily to one show: "Ghost Hunters" on the Syfy Channel. "Ghost Hunters" is to the paranormal field what Sugarhill's "Rapper's Delight" is to hip-hop -- it launched a subculture. The show was developed by Craig Piligian, founder of Pilgrim Studios, which created reality shows like "American Chopper" and "Dirty Jobs." The show was launched in 2004 and remains the Syfy Channel's top-rated paranormal reality show.
Piligian says he was inspired after reading a New York Times story about two Roto-Rooter plumbers who also offered house calls to fix paranormal disturbances.
"The same qualities they used to fix a leaky pipe they used in their work to debunk whether or not a place was haunted," Piligian says. "It was almost mechanical in nature, and not so much voodoo."
Jason Hawes is one of those plumbers and now the no-nonsense star of "Ghost Hunters." A gruff guy with a shaved head and goatee, he's also the co-founder of the Atlantic Paranormal Society. He's feted at paranormal conferences, speaks at corporate events and has written seven books on his ghost-hunting experiences.
"The fame is great, but the minute I'm done filming, it's all about my family," says Hawes. He and his wife met in junior high and have five children. "I'm still a little plumber from Rhode Island."
Hawes said the popularity of paranormal shows has added visibility to the field, but that some shows have damaged its credibility because they don't take a scientific approach to cases.
He won't name names, but he says some shows launch investigations assuming a place is haunted and allow cable production companies to handle evidence, which he says leaves room for fabrication.
"Ghost Hunters" won't allow the Syfy Channel to touch any evidence, and nothing on the show is fabricated, he says.
"A lot of our cases never air," Hawes says. "We go in believing that 80% of all claims can be disproved."
Hawes, Bagans and other paranormal stars may be famous, but there's one ghost-hunting duo that stands above all the rest: Lorraine and Ed Warren, the couple depicted in this year's Hollywood film, "The Conjuring."
The husband-and-wife team were investigating ghosts before it was hip. They founded The New England Society for Psychic Research in 1952 and investigated the notorious paranormal case that inspired the book and film "The Amityville Horror."
Ed Warren died in 2006, but Lorraine, who was portrayed by Oscar-nominated actress Vera Farmiga, discovered during a recent trip to the pharmacy that she's a celebrity herself.
"I had to pick up my prescription and the first thing they said was, 'Lorraine, you're a movie star!'"
When she left a premiere of "The Conjuring," she says she was surrounded by fans who wanted to know about her work.
Some asked if "The Conjuring" exaggerated all the spooky things she encountered.
"Maybe certain dramatic things, but not the important things," says Warren, at 86 a buoyant woman who calls strangers "honey" and seems tickled by her fame. "I'm very proud of it."
Warren is a devout Christian who says she became a paranormal investigator to bring people closer to God. "The Conjuring" is filled with chilling moments, but she doesn't consider herself brave.
"I'm brave in my faith," she says. "That's where my bravery comes from."
Their most terrifying cases
Thanks to TV shows and movies like "The Conjuring," paranormal investigators say they've never been busier.
Claudia Lee, director of Roswell Georgia Paranormal Investigations, says she has seen a "tremendous increase" in requests for help. When she and her investigators arrive at people's homes, their clients easily slip into the ghost-hunting jargon they've heard on TV -- talking about feeling "cold spots" or seeing "orbs" of floating lights.
Lee says the paranormal shows have created "mass hysteria" -- people think something paranormal is going on in their home when the explanation is often mundane.
"We will often get a call with clients that are convinced that the dust particles in their photographs are actual demons," Lee says.
Some investigators say that there are times, though, when they encounter something that is terrifying.
Lee says her team met a single mom who was being "oppressed by some type of demonic activity." A priest was called in to perform an exorcism.
"When he arrived, the client's eyes were all black," she says. "The eyes were crystal blue when the priest finished."
Lee says she didn't sleep for weeks after that case, which was eventually filmed by the Discovery Channel as "The Exorcism of Cindy Sauer" (It's on YouTube).
"You never know what you're going to walk into," Lee says. "I have never seen anything like that in my life. I thought maybe I shouldn't do this."
John Zaffis, a paranormal investigator for 38 years, has walked into his share of strange situations. He's been dubbed the "Godfather of the Paranormal" and hosts the television show "Haunted Collector." He's Lorraine Warren's nephew, and his investigations have been featured on the Discovery Channel and "Unsolved Mysteries."
Zaffis says he's been attacked.
"I've been scratched, I've been burned. I've seen people levitate. I've seen people's eyes change, and I've seen people thrown around," he says. "That changes how you look at things."
Noah Voss, a paranormal investigator for 25 years who sells ghost-hunting equipment at GetGhostGear.com, says the job requires not just courage, but sensitivity as well. People share experiences with him that they don't even reveal to their spouses.
"I've had guys bigger than me break down and cry, saying to me that they can't go back into their house because it's haunted," says Voss, who is 6-feet-4 and more than 200 pounds.
But Voss and others say those moments of terror are not routine. Some compare it to fishing: There's a lot of preparation, but nothing usually happens. It's not like TV, where a ghost appears in every episode.
Some of the newer ghost-hunting groups aren't prepared for the mundane nature of actual paranormal investigations and worry that they might miss out on their big chance, Voss says. "People will say, 'My group has been investigating for six months and we still haven't had our own TV show.'"
Some inexperienced teams give new meaning to taking their work home with them, says "Uninvited" author LaChance.
"Novice teams will try to provoke spirits, and the next thing you know these things follow them home," he says. "About two years ago, we had more investigative teams calling us to help them than individual families. It was crazy."
LaChance wishes he did not believe in the paranormal.
He investigated one case involving a couple's 50-pound pit bull. The couple had treated their dog like it was their child. But when he showed up, the dog was inside its cage, dead. Blood was everywhere. He says an entity had thrown the dog, cage and all, down the hall and killed it.
Like some other paranormal investigators, LaChance talks about his work like it's a ministry. Many ghost-hunting teams don't charge for investigations. They see their work as a way to help people in distress.
"It has to do with helping someone else who is in the same situation I found myself in at one time," he says, recalling the house where he says malevolent spirits attacked his children. "When I went looking for help back when I needed it, I could not find it."
Zak Bagans meets a ghost
Back at Victoria's Black Swan Inn, Zak Bagans has his own encounter with an unexpected "visitor." It happens during the second episode of the show's eighth season.
As Bagans stands in a darkened bedroom, he learns from the inn's owner that her mother recently died in the same room only months earlier. The owner, Jo Ann Rivera, asks Bagans to summon her mother's spirit and ask her to say something that would establish her identity.
Nothing happens at first. As he stands in the deserted bedroom, Bagans tosses questions aloud at Rivera's mother while holding a recording device.
Bagans then jumps because he says he feels something enter the room. He rewinds his electronic device and pushes the play button.
The TV camera's microphone picks up the faint voice of an elderly woman saying an odd word: "Bossier."
"Bossier," Bagans says to Rivera. "What is that all about?"
Rivera is stunned. Her eyes widen, and she starts to cry. Bossier is Bossier City, Louisiana.
"Bossier is where she liked to gamble," Rivera says of her mother. "That's where she wanted to go before she died. Nobody knows that word except for me."
Rivera's voice cracks, and she wipes tears away.
"I'm sorry," she says, embarrassed by her emotion.
"Don't be sorry," Bagans says as he hugs her.
Later, Bagans says cases like these are why he became a paranormal investigator. "To help people like her, to get evidence like that -- you cannot deny that evidence."
Sure you can, say skeptics, who question whether such scenes are real or simply a bid to boost ratings.
"There's an old saying," says Zaffis, the "Godfather of the Paranormal." "To the believer, we have an overabundance of evidence. To the nonbeliever, we never have enough."
The encounter certainly appeared to leave its mark on Rivera, the owner of the Black Swan Inn. In Bagans' "Ghost Adventures," she was a shaken woman whose family was under attack by demonic entities.
Go online, though, and Rivera seems to have recovered. She posted an online essay entitled, "Yes, I Live with Ghosts!" Rivera announces that her inn is haunted and offers access to ghost-hunting teams. It's also advertised as a "world-class wedding venue" that stages more than 20 weddings each year.
In an interview that accompanies her post, a smiling Rivera adds that she's taken on another job title:
She's now a paranormal investigator.