In my latest book, Trail of Terror: The Black Monk of Pontefract, Cripple Creek Jail, Firehouse Phantom, and Other True Hauntings, I spend several weeks investigating a diverse range of supposedly haunted locations across the United States and Great Britain. As a paranormal investigator, one of the questions I'm most often asked is: "Just why would a place be haunted in the first place?"

The answer to that question varies from place to place, and usually involves a number of complex factors that involve people, events, and different forms of energy. Typically we see three broad categories of haunting: haunted people, haunted places, and haunted objects. One, two or even all three of them may be at work when a paranormal investigator is called in to conduct research.

There is a popular misconception that a place usually becomes haunted because of some dark and terrible events that took place there. While this can often be true—hence the number of haunted battlefields, asylums, and places in which murders took place—it is not always the case. Consider the Denver Fire Museum, once one of the oldest fire houses in the Mile High City and now home to the Denver Fire Department's collection of historic artifacts and memorabilia.

It was a privilege to be invited to spend several nights there, investigating claims of shadow figures, phantom footsteps, and other bizarre phenomena. Some of the items on display at the museum have sad, even tragic back-stories, such as the mattress on which a victim died in a residential fire (the charred outline of their body is still visible) and the cross made from two girders taken from the World Trade Center in the aftermath of 9/11. One can only imagine what kind of energies they contain.

Firefighters encounter a great deal of death and trauma while going about the course of their duties, and it is my belief that some of that leaves a residual "psychic scar" sometimes—one that can be detected at a later time, and perceived by eyewitnesses as paranormal activity.

Yet flip it around and take a look at this from the other side: a firehouse is often one of the happiest places on Earth (I speak from experience, having served in one for fifteen years). The men and women who work there become very close; in fact, they often consider one another to be family. By extension, the firehouse becomes a home away from home. Think of the sheer amount of warmth, happiness, and positive energy that is generated there. Some of that energy lingers, long after the firefighters have left for the last time, and that is a potential source of great power that can be used to manifest paranormal activity.

Another location that I investigated for the book was the London Underground, which has a long and well-documented history of ghost stories associated with it. Speaking to staff members, often on the condition of anonymity, I heard stories of ghostly apparitions walking the tracks at night and disembodied footsteps pacing along the platforms of deserted stations long after the last trains had stopped running.

The London Underground has no shortage of death and tragedy in its past, having seen fatal train crashes and a truly horrific fire at King's Cross Station. There are also ongoing suicides and accidental deaths that unfortunately continue to claim still more lives. There has also been at least one murder, the stage actor William Terriss in the vicinity of Covent Garden, whose ghost has been sighted on more than one occasion.

Tens of thousands of Londoners travel via the Underground (or "the Tube" as they prefer to call it) every day. Some are happy, others are sad; taken in their entirety, this is another source of collective energy that might be used to fuel the paranormal activity that so many report taking place in the tunnels and at the stations. One particularly outlandish urban legend involves a group of subterranean dwellers—"mole people," if you like—that are said to live in the depths of the tunnels, never seeing the light of day.

Poltergeist outbreaks are among the more bizarre and spectacular type of haunting. They are relatively rare, and tend to be the equivalent of shooting stars on the paranormal landscape, blazing brightly and intensely for a short period of time (usually months to a year or two) before fizzling out and disappearing. One of the most aggressive and disturbing poltergeist cases ever documented was the infamous "Black Monk of Pontefract."

The Black Monk, or "Fred" as he later came to be known, terrorized an innocent British family, the Pritchards, in the town of Pontefract throughout the late 1960s. They lived in an ordinary house in an ordinary neighborhood, one not so different from yours or mine. The haunting began when a fine, granular powder began to fall down from the ceiling, covering those present in a chalky substance that was never identified. Remarkably, it seemed to be falling from somewhere beneath the ceiling, rather than coming from it, as though originating in some other dimension.

Things escalated quickly after that. Objects seemed to take on a life of their own, moving about the house without anybody touching them. A plant removed itself from its pot and floated serenely up the staircase, as though held by an invisible hand. On hands and knees while cleaning the fireplace one morning, Mrs. Pritchard was startled when a shower of keys suddenly rained down all around her. Footsteps were heard in empty rooms. Banging and knocking sounds echoed from the walls and ceiling. Doors opened and closed themselves.

The figure of a tall, dark figure wearing a hooded robe was seen emerging from a closet in the master bedroom. The Black Monk was apparently not afraid to show himself.

Then he turned violent.

The house had an internal bunker, known as "the coal hole" because it was used to store coal for the fireplace. Mr. Pritchard was in there one day when the door slammed itself on him and refused to open, trapping him inside in absolute darkness. He then sustained what can only be described as a physical assault from a spirit entity, one that left him, in the words of those who knew him personally, "a changed and broken man."

Not content with attacking the man of the house, Fred then turned his attention to the family's eldest daughter, dragging her upstairs kicking and screaming while her parents could do nothing but look on with horror.

When I moved into the Black Monk House for a week in 2016 to investigate it, I didn't quite know what to expect. Experience told me that the poltergeist itself should be lone gone, and yet the house had generated consistent reports of paranormal activity for the past fifty years, and things had REALLY kicked into high gear when a movie (When the Lights Went Out) was made about the case, generating renewed public interest, an influx of visits from paranormal investigators—and me.

Fred wasted no time in welcoming me. I walked in to find that a mirror that had hung on the wall undisturbed for many years was now lying on the floor at the base of the stairs, cracked and shattered. The house had been locked and empty at the time the breakage occurred. This was just the first of several paranormal phenomena that I was to encounter during my stay, many of which are described in Trail of Terror.

Why was the Black Monk House haunted? The house sits on the site of an orchard that was once tended by local monks. An old story alleges that a particularly heinous monk raped and murdered a young girl on the site, throwing her body down a well that sits underneath the house. The monk was then said to be hanged on the spot by vengeful villagers. While a fascinating and spine-chilling tale, there is no historical evidence to support it. What we CAN say for certain is that the battle of Chequer Field was fought on the very same land, and battlefields are of course well known for being haunted. My investigation into the case is still ongoing, and for every answer that I find, another handful of questions are raised.

This, in a nutshell, is why paranormal field research is so maddening and rewarding in equal measure.

Long may it remain so.