It was late in the afternoon, while leading his last daily tour of the historic Mark Twain House, that Jason Scappaticci glimpsed something that would change his thinking about the paranormal.
Assuming it was a visitor who had separated from the group, he walked over. But instead of finding a stray guest, he says he found a supernatural one – a transparent figure of a woman dressed in a hoop skirt floating down the hallway.
"It was definitely a ghost," Scappaticci said. "I just stopped in my tracks and froze for a second and stared at it."
For four years, Scappaticci, 28, has worked at the Hartford, Conn., home of the famed American author Samuel Clemens. He had heard other tour guides whisper about voices they'd heard in the hallways, but said he was a skeptic until he had his own experience a few years ago.
Since then, other guides, visitors and security guards have come forward to tell their own stories of unexplained encounters in the 19th century Victorian mansion.
Some hear voices, others laughter. Some see apparitions of women, others visions of young girls. All swear spirits of the Clemens family haunt the house.
Though many dismiss such claims, a growing group of people around the country is embracing them – so-called paranormal investigators who, in many cases, employ souped-up technology and science-inspired methodology to search for evidence of the supernatural in historic sites like the Mark Twain House to seemingly ordinary homes and every place in between.
Jason Hawes, 37, and Grant Wilson, 35, stars of cable channel Syfy's "Ghost Hunters," estimate that there are thousands of paranormal investigators around the world.
The Rhode Island-based Atlantic Paranormal Society, which Hawes founded in 1990, now has a group in every U.S. state and 12 other countries around the world. The pair acknowledges that their show and others like it have given the ghost hunting community a boost in numbers and profile.
"There are a lot of people out there who believe that they're having problems and need someone," Hawes said.
Though they don't like to discuss the details, both men say they've had personal paranormal experiences that push them to help others.
"It's good that they know that people like us are out there. We do this for free," Hawes said. "We want to empower them and give them their homes back and their strength back and their lives back."
With a puckish nod to his pop culture predecessors like "Ghostbusters," he added, "Who else are they going to call?"
But though they hunt for the supernatural, they say they retain a healthy dose of disbelief.
"We are skeptics, otherwise we would believe everything," said Wilson.
The most interesting cases make it onto the show, but Hawes said they're able to debunk 80 percent of the claims of the paranormal.
After interviews with their clients, the investigators reach into their trove of ghost hunting technology.
Electromagnetic field meters detect spikes in electromagnetism that could cause some people to hallucinate and imagine spirits that aren't really there. Digital infrared cameras capture images that are invisible to people.
Surveillance cameras record 360 degree panoramas of rooms thought to be inhabited by ghosts.