As sunlight faded, so did the dour faces staring from dark paintings on the second floor of Stone's Public House, their images disappearing from view.

Sounds of Main Street below seemed miles away, yet the 1830s-era inn was alive with noise. Its wooden floorboards creaked and voices echoed from the musty attic.

The racket came not from a ghostly little girl that customers say they have seen lurking at the windows upstairs, nor other spirits whose legends give Stone's its reputation as one of the most haunted spots in New England, if not the country.

It was a woman setting up a night vision camera upstairs, chatting with a friend as he waved a blinking electronic device over the wall. Two men spread a tattered dress on a table nearby, talking as they scanned the garment with infrared lights.

Three teams of paranormal investigators descended on the restaurant Monday night to probe the spooky stories about the Ashland landmark, which is home most other nights to non-scary food, drinks and live music.

It was far from the first time ghost enthusiasts explored the old inn, with doors that refuse to stay shut and employees who say they have felt invisible hands. The group's guide, David Retalic - an Ashland firefighter who investigates the paranormal on the side - has studied the building at least three times. It was featured on the Sci-Fi channel's "Ghost Hunters" show in 2005.

But this marked the most thorough exploration of the building yet, Retalic said, and may have been one of the biggest joint ventures ever in the world of ghost hunting.

"As far as I know, this is the first time three groups have ever gotten together on the same night to investigate the same place," he said.

Jeff Belanger, a Bellingham resident who runs the Web site ghostvillage.com, said the effort was unusual because people who investigate the inexplicable often can be territorial and competitive.

"So many groups are so catty," Belanger said. "It's like 'West Side Story,' but much less cool."

Retalic credited Belanger with the idea for Monday's investigation.

Among those poking around the building with tape recorders and cameras was David Francis, an Upton resident. He said he is seven chapters into a 10-chapter book on Stone's history and reports of eerie phenomena.

"They've come from customers, they've come from people that passed by on the street, law enforcement officials," Francis said. "It's not just a place that's trying to market ghosts to get people in the door. There's really something going on."

However, Francis is trying to separate fact from myth. He said he's dug deep in historic records to verify stories about the inn, dispelling some stories, confirming others and discovering new ones.

Death records show it is true that a little girl was once killed by a train near Stone's, he said. But Francis said there is little evidence to confirm a salesman named Mike McPherson ever existed, much less killed over a poker game gone bad.

Francis said he has confirmed four deaths in the inn itself. Records say William Alfred Scott, who owned the inn from 1858 to 1904, lost two sons to cirrhosis of the liver and one to "general paralysis," and his wife died at Stone's as well, he said. News articles say one of his sons attacked a woman at the inn between 1894 and 1895.

Francis' first paranormal experience came age 10, when he saw a faceless apparition sitting on his brother's bed. He brushed off the experience until later in life, when he was shaken by a few more inexplicable incidents in his own home.

Francis said he joined a Worcester-area paranormal investigation group in 2006, but recently went solo with his work.

"The more I got active, the more I realized that I didn't want to find answers for stuff that was going on in my home," Francis said. "I just wanted to be able to get out and help people who didn't have the answers."

Stone's Public House has been an interest for years.

"It was something we talked about in high school over the lunch table," Francis said.

Bradley Reed also grew up on those tales. His student group, the Paranormal Investigation and Research Organization, traveled from the University of New Haven to aid in the investigation Monday.

Reed's mother, Sharon, is originally from Ashland, and recalled trying to push open the door of a bathroom stall and feeling some unseen person on the other side, pushing back.

"It scared the death out of me," she said Monday.

Reed said his grandmother had a similar experience and he's been interested in the inn ever since. His group's motto is "truth through science," he said, and they use everything from infrared cameras to electromagnetic field monitors to look for unusual signs in places people have reported ghosts.

Also along for the ride were Carl Johnson and Laura Casey of New England Anomalies Research and Investigation. Johnson appeared on the first two seasons of "Ghost Hunters" as a "demonologist."

Cliff Wilson, president of the Ashland Historical Society, tagged along Monday and said he's been working on a history of the inn with Francis. The historical society lacks a complete story of the building's past, he said.

The hunt for proof of ghosts ties to bigger issues, Belanger said - faith, belief, history.

"These are people trying to wrap their hands around a very big question and find their own answers," he said.

The groups said they need to review the data they collected before making any conclusions. Francis said he hopes to organize a night at Stone's to discuss the results.

(David Riley can be reached at 508-626-3919 or driley@cnc.com.)