Halfway down the cellar steps at the Grandstreet Theatre, the electromagnetic meter detected an unusual presence.

The air grew unusually cold. Conversations stopped.

"We set up cameras with infrared devices and motion detectors," said ghost hunter Karen Stevens. "We did detect some unusual phenomena."

Stevens is the author of "Haunted Montana: A Ghost Hunter's Guide to Places You Can Visit," released this month by Riverbend Publishing in Helena.

The specters Stevens hunted ranged from little Dorothy Dunn, who haunts the Meade Hotel in Bannack, to Clara Bicknell Hodgin, who wanders Helena's own Grandstreet Theatre.

"The story is that Grandstreet is haunted by a woman who was the wife of the minister when the building was used as a church at the turn of the century," Stevens said. "There have been a number of different phenomena reported there."

Stevens has personally investigated each haunted site over a period of years. She interviewed witnesses to each haunting and, in some cases, used ghost-hunting devices to track the phenomena.

In her new book, the first of two, Stevens lists the history of each location and its ghostly activity. She also ranks the activity from "high," such as the Little Bighorn Battlefield, to "low," like the Rookwood Speakeasy in Butte, where the ghosts of two men continue to startle visitors.

"I grew up in a haunted house," Stevens said. "I've been fascinated by ghosts all my life. I started collecting Montana ghost stories about 30 years ago. It's been absolutely fascinating, collecting the stories and talking with the people."

Stevens' new book taps the growing interest in ghost tours and haunted vacations. Tourists from Montana and beyond have booked tours across the state, hoping to catch site of an elusive specter.

"We've offered 25 tours in the last two weeks," said Renee Christiansen, owner of Fun Adventure Tours in Billings. "Last year we offered 20 ghost tours, so we're up five tours. When we started, we offered just three tours on a Saturday afternoon."

Closer to home, Lee Holmes, owner of Last Chance Tours, also has capitalized on the popular ghost tours.

His sundown adventures take riders across town, stopping at haunted locations and eerie, moon-bleached graveyards.

"It's hugely popular," Holmes said. "We ran 10 ghost tours this year and they all booked out. They booked out two weeks in advance. We didn't advertise one bit -- it's just word of mouth."

The local ghost tours, led by historian and ghost-writer Ellen Baumler, pass through downtown, Catholic Hill, the Grandstreet Theatre, Carroll College, and the Benton Avenue Cemetery, among other spooky haunts.

"There's such a demand," Holmes said. "We even do them in the summer time now. People have a real fascination with that supernatural part."

While her travels are many, Stevens recalled one tour of the Arts Chateau in Butte, where the ghost of a woman has been seen, objects have been moved, and strange sounds linger in the night.

The activity, she said, is moderate. The encounter, she added, was close enough to leave the ghost hunters shivering.

"We had a rather eerie experience there," Stevens said. "We stepped into a column of frigid air at the top of the stairs. It's one of the most common phenomena you find in haunted places. People feel extremely cold."

The theory, Stevens said, is that the ghosts are using the energy of living people to materialize.

"Our guide once heard what sounded like someone crashing their fists down on a piano in the ballroom," Stevens said. "He turned into a believer after that."

For more information on Stevens' book, log on at www.riverbendpublishing.com.

Reporter Martin Kidston: 447-4086 or mkidston@helenair.com