Under the cover of night, tucked away in the enlisted men’s quarters, a raspy robot utters the word “poltergeist.” Utterance is heard clear as day with the help of Paranormal Puck — an investigative tool that paranormal investigators are using this evening to detect the presence of supernatural spirits in Fort Knox. The software is the latest gadget in the toolkit of 207 Paranormal, a nonprofit Bangor-based group that gives ghost tours of the 19th century fortress straddling the western bank of the Penobscot River in the town of Prospect.

After sunset, Paul Wolfe and other guides lead the way through the dark, narrow passages of the sprawling, granite fortification completed in 1869. Maine’s first fort, the fortress was built to protect the Penobscot River Valley towns from British naval attack. Ghosts are not the only apparitions encountered as part of the tour. Bats also inhabit the fort. The winged mammals fly overhead in one of the many dark, cave-like rooms. Tour-goers are forewarned about getting “bat-slapped” by the harmless creatures and advised not to “zig or zag too much.”

Ghost tour participants had their phones at the ready to capture images of Mike, Elizabeth, Leopold Hagy and other spirits said to inhabit the former military outpost and its grounds. OUT & ABOUT PHOTOS BY MAGGIE TROVATO

“We believe that spirits can manipulate the environment around this device to create a word that comes through,” Wolfe, a radio broadcaster by day and paranormal investigator by night, told the tour group. Wolfe’s first supernatural encounter was being awoken by a woman, clad in a white dress, in the dead of the night.

“I started hearing the spirit start humming. It turned into a scream, and I was out,” Wolfe laughed.

Besides the ghost tours, 207 Paranormal’s 11-member team conducts ghost investigations free of charge in Maine. The team even does house calls.

“We want to be there for people,” Wolfe said. “I’ve lived in a haunted home before … I know that helpless feeling you can get.”

Acting as a connector to the spirit world, the puck allows investigators to text the spirits via an app. The device detects changes in temperature, humidity and static electricity, among other things. When a presence is detected, and the ghost replies, their response takes the form of an automated voice slightly more eerie than Siri’s.

The military outpost never saw action, but a few people did meet their demise there. Their spirits are said to dwell in the passageways. Among them is Leopold Hagy, the fort’s former caretaker. A dark, shadowy figure has been spotted as though he is making his rounds.

“Two-Step Alley,” as the narrow passage is called, adds to the atmosphere for tour-goers navigating bats and spirits at Fort Knox in Prospect.

Another spirit, who has identified himself simply as Mike, died during the fort’s construction. The story goes that the fellow was sitting on a keg of black powder and smoking a cigar. When warned of the danger, Mike dismissed the warning. To show there was no danger, he is said to have touched his cigar to the black powder — causing an explosion and his untimely death.

A young girl named Elizabeth, who lived on the land before the fort was built, likes to play with toys that the investigators bring. Cat toys will light up from what they think is her touch. On this particular tour, one participant reported the sensation of the little girl hugging her legs.

Wolfe recalls his first experience, feeling the spirits come alive, after dark at Fort Knox.

“The spirits certainly come alive, and, sure enough, I was able to interact,” he remembers. “I was hooked; Absolutely hooked from there on out.”

When the tour ends, the sun set long ago. The only light is the moon, the stars and a couple of flashlights. Visitors are given time to roam the fort and do some investigating of their own.

Fort Knox is located at 740 Fort Knox Road in Prospect. The ghost tour costs $35 per person. Proceeds benefit the fort. To make reservations, visit fortknoxmaine.com. For more info, call 469-6553 and email info@fortknoxmaine.com.