Groton — To Shamus Denniston, ghosts don't look like a white sheet with holes cut out for eyes.

They look like slight disturbances in an electromagnetic field, a shadow in the corner of a camera frame or objects flying off shelves.

Or they don't look like anything at all, only alerting the living of their presence with low murmurs or knocks on the wall.

Denniston, along with the other members of the Thames Society of Paranormal Investigations, arrived at a Groton office Sunday night with all the equipment they would need to record a spirit living there.

Hours after night fell on Sunday, the team unloaded handheld cameras, tripods, voice recorders, electromagnetic field readers and air meters.

Denniston’s wife, Sophia, works in the offices of the safety education company Survival Systems USA, which occupies a hangar-like building built in 1999 near Groton-New London Airport. She said employees there have been reporting weird noises and inexplicable events for years.

"In their mind, there's something in there," Denniston said. "They said different employees over the years have experienced something strange."

One employee apparently saw a picture fall off a wall. Another felt objects being thrown at them, and Sophia Denniston reported hearing a man humming and singing when she was alone in the building.

Survival Systems' CEO Maria Hanna has named the ghost causing all this "Fred."

Denniston founded the Thames Society of Paranormal Investigations in 2005. He had been a member of several other local paranormal groups but was frustrated that they never followed through with clients to either rid properties of spirits or explain what they were seeing and hearing.

"My focus ... ultimately was to help people," he said. "They just want to know that what they've been experiencing is not crazy — that they're not crazy."

Denniston would know. He said he grew up in a house in Montville haunted by disembodied voices, a baby grand piano that would play on its own and shadowlike figures looming over his brother's bed.

Denniston said even his father, a former police officer, saw a human silhouette in the house when he was home alone.

"When we got home and found him he was scared," Denniston said. "My dad wasn't someone who got scared."

In the past decade he has assembled a team of “like-minded people” to investigate reports of paranormal activity, mostly in historic homes or museums in Connecticut. He said a healthy dose of skepticism is healthy while ghost hunting.

“I’m usually looking for … people who are objective,” he said. “We don’t necessarily take everything at face value.

They have travelled to Massachusetts and New York to investigate ghostly reports and are planning a trip to New Hampshire next summer.

They don't charge their clients and pay for their equipment with their own money or with donations raised through fundraisers or public demonstrations. The group takes about two clients a month.

Denniston said about half of those investigations turn up something paranormal.

"To me, that's something that cannot be explained through scientific or logical means," he said.

The group's website uses similar terms.

"We travel throughout New England and beyond in search of the supernatural," the homepage announces in large white letters on a black background. "We conduct confidential and objective investigations. We strive for tangible, measurable evidence, to provide our clients with answers."

Larger blue letters on the right side of the page link to the Thames Society of Paranormal Investigations' online store, where visitors can pick up two-way radios, books of local ghost stories or a pack of Halloween-themed cookie cutters.

The team assembled outside the Survival Systems offices Sunday night, unloading boxes of equipment into a conference room inside. Stephanie Sutera, of Waterford, said she’s a longtime member of the group and a lifelong believer in the supernatural.

She said she captured her most convincing evidence of a ghost a couple of years ago, in a photograph that she said appeared to show a man’s torso and face.

“That was a good one,” she said.

Denniston said his most recent scare was a phantom arm grabbing his shoulder in a house they were investigating.

The team was planning to be at Survival Systems all night, capturing sounds and images on as many cameras and recording devices as they could set up all over the building. They set up two cameras on the deck of the company’s pool, which employees use to simulate water rescues.

They would then spend more than six hours monitoring the building’s creaks, bumps and electricity levels, and asking the ghost — whoever it was — to answer questions.

“We’ll typically introduce ourselves, and ask for them to identify who they are,” he said. “To an outsider it may look like we’re talking to thin air.”

Garrett Fernando, 22, is the group’s equipment manager. He joined up after meeting Sutera, figuring he could contribute his video experience. Sunday was his first investigation.

“I’m a little bit skeptical,” he said. “But I like to keep an open mind.”

m.shanahan@theday.com