Few have seen the purported ghost of a little boy riding his tricycle up and down the long basement hallways of the Old Main building on the Skagit Valley College campus in Oak Harbor.

But there are some who are convinced he’s there.

On Thursday night, ghost hunter Ross Allison went looking for the boy.

Allison is a University of Washington professor, author of multiple novels and founder of AGHOST. He is the only full-time ghost hunter in the Pacific Northwest.

Allison led a ghost tour of the bottom floor of Old Main, formerly the Navy hospital, commissioned in 1942.

Participants on the tour, ranging from students and educators to curious community members, held a thermal scanner, designed to pick up changes in temperature; a compass; and an electromagnetic field detector. It’s believed that spirits disrupt the electromagnetic field in such a way that a ghost hunter can tell one is present. Allison also brought a device that displayed a green, laser-produced dot grid, which fluctuates in pattern when something is detected.

Also armed with cameras and voice recorders, Allison led the group through areas where the little boy on his tricycle was reportedly seen.

The thermal scanner soon picked up cold spots in the shape of footprints under a water fountain. The laser grid distorted to support the scanner’s detection. Allison pointed his ultra-violet light on the spot so the first-time explorers could see.

Then the footprints were suddenly gone.

Allison, who came to Skagit Valley College following an invitation from Student Life, had started the evening in the basement of Old Main with a presentation.

“I believe there’s something out there,” Allison said.

“You need to experience it for yourself. I’m just trying to open your minds.”

Allison said keys to being a good ghost hunter are passion, devotion and patience.

Also important are honesty, education, an open mind and skepticism, he said.

Allison said he doesn’t rely on devices like Ouija boards and pendulums because someone has to be holding them. And when he invites psychics on expeditions, he doesn’t tell them anything more than if the building is a residence or a commercial building.

Allison said he takes a scientific approach to ghost hunting.

“You can’t use the paranormal to prove the paranormal,” he said.

Allison, who has researched the paranormal for more than 25 years, has appeared on MTV, the Syfy channel, the Travel Channel, ABC’s Nightline and TLC.

“I blame my mother,” Allison said, adding that she loved to tell him ghost stories.

Allison founded Advanced Ghost Hunters of Seattle-Tacoma, or AGHOST, he owns the Spooked in Seattle ghost tours, and has taken on more than 700 cases. Recently, Allison returned from a case in Hong Kong.

Allison posed the question of why ghosts wear clothes.

“How you see yourself, you project yourself as a ghost,” Allison said.

So since people rarely imagine themselves naked in their minds, they won’t appear naked as ghosts.

People create their own perceptions, and that is what scares them, he said.

As he continued his walk through Old Main, Allison led  the group into a teacher’s office, and the EMF detector picked up higher-than-normal readings about three feet off the ground near a desk with marbles on it.

Allison asked aloud if anyone was in the room.

The investigators then headed into the bathroom, making sure to close the window.

The green laser grid covered the walls, remaining normal in pattern. Allison asked if the spirit could let the group know he was there.

Allison asked the ghost to flush the toilet — nothing. He asked if the ghost wanted to play with the marbles — nothing.

The investigator with the EMF detector walked around the crowded bathroom, looking for spikes in the reading.

The detector suddenly spiked in a corner near the paper towel holder, the reading held steady in an area behind a scared woman from the group. The woman moved, and the EMF detector reading went back to normal levels.

“It’s our own imagination that scares us the most,” Allison said.

“We’ve been obsessed with death since the beginning.”

Ross said that one in five people believe they’ve had experiences with the paranormal.

Kayla Roeseler, who works at HomePlace in Oak Harbor, which specializes in Alzheimer’s and dementia care, said she has had a couple paranormal experiences at work.

One time, she said, “I heard a voice go, ‘Hey.’ And I was like, did that really happen?”

But she said she wasn’t scared after her experiences. She said that having dementia is confusing. And she said the ghosts “are just here to find those answers they didn’t get when they were alive.”

Oak Harbor resident Laura Honeycutt, her husband, Ben, and her daughter have all had experiences with ghosts.

“I have seen ghosts since I was small,” Honeycutt said.

“So has my daughter.”

She said there’s family history that some of her family might have been witches in Salem during the witch trials in Massachusetts in the 1600s.

Honeycutt and her family have seen ghosts in Virgina, Wales and Oak Harbor, among other places.

“My husband met his ghosts in New Mexico,” Honeycutt said.

She said some ghosts are new, some are repeated. And some she doesn’t recognize, while others she does, including her father, who died when Honeycutt was small, she said.

“It was sad,” she said. But she added that she wasn’t scared with him.

After the tour, Allison took questions from the crowd that packed the student lounge in the former hospital.

Allison was asked if he is ever scared to go home or needs to sleep with the lights on after an expedition.

Allison said that with the exception of St. Louis University, which inspired the movie the “Exorcist,” he doesn’t get scared.

He said the movie is based on a little boy, Robbie (whose name has been changed), who was exorcised in the church building at the university campus.

When Allison went there, he saw the room on the fourth floor where Robbie had stayed covered with dozens of dead birds. When he started his investigation, all his detectors and devices picked up higher than normal readings.

While no definitive evidence of such an aggressive ghost, or any ghost, was found Thursday night in Old Main, the Oak Harbor campus has been featured in Allison’s book “Ghosts on Campus — Stories of Ghosts that Haunt Students.”

A final group member asked Allison if he ever gets a feeling that there’s a ghost in a building or senses something.

As the lights came on in the hallway, Allison said he “definitely gets a heavy feeling.”