Claims of local paranormal activity fill the spectrum between intimately human ghosts, tied to old houses by their mourning for lost love, and gaps in the laws of nature where no man has ever set foot. The vast majority of claims are made by local pranksters and charlatans. The very few truths are especially threatening because they are localized. Spatial stability opens a mystery to scrutiny and further discovery.

If you suspect a significant threat, steer clear and prevent public access until you have attempted a preliminary investigation of the location's history. Do not merely avoid entry. For your safety, assume that localized phenomena are limited by something other than mundane building materials, cave entrances or property law, if they are limited at all.

How do I learn the history of a plot of land?

A document of the transfer of ownership of land is called a conveyance. These are a matter of public record. The local archive is typically maintained by the county's recorder of deeds, or a less specialized local equivalent to that office, such as the county clerk. The site is often the county courthouse.

To look through conveyances relevant to a given property is called a title search. Besides answering the question of who actually owns the land, such a search may reveal other stakeholders, typically in the form of liens, as well as financial difficulties, such as mortgages and back taxes associated with the property.

Detailed property tax records are available from the county assessor. Taxes are levied on the basis of this official's opinion on property values from year to year. In the event of untaxed developments on the land, such as obvious discrepancies in building floor space, the owners are likely to have carried out modifications without a permit.

Some communities maintain archives with old photographs, building plans, maps and newspaper clippings. These could be the property of local historical societies, the town hall, or a local library or museum. Experts maintaining such collections will generally be knowledgeable about supposedly paranormal activity.

How do I find floor plans?

Starting in the cities, detailed plans have gradually come to be required for building permits. Plans are archived, as part of these permits, by the local building inspector. For older houses, more research is required. Knowing when a house was built, or when it's been up for sale, is useful in any such effort.

Common American homes were built without detailed specifications up to the early 20th century. Instead of blueprints for an individual house, builders had mail-order kits recognizable from Sears, Roebuck & Co catalogs, or pattern books and the conventions of their trades. Popular house plans from the late 19th century can be found in the books of Palliser, Palliser & Company of New York, or others in the business. Real estate advertisements in archives of local publications—including newspapers, farm journals and women's magazines—will also tend to show the floor plans of local houses when they change hands.

Even today, houses in major residential areas are often built from generic plans. Even if these plans cannot safely be found on paper, a basic familiarity with a property under investigation may be acquired by entering similar houses in the neighborhood. By the same token, one apartment tends to be similar to those directly above and below it.

The developer of a property, if it is still in business, could have the original plan of a building in a private archive, even if no copies were filed with the local government. Otherwise, fire insurance maps from the time of construction will tend to show the plan in a simplified format, or at least the building's principal construction materials. Analysis of low-altitude aerial photographs are another possible substitute.

What else can I learn before entering?

Run background checks on current residents and owners. If local allegations of paranormal activity are persistent across multiple generations, track down former residents to test the anecdotes. Phone directories organized by address were not common before the Internet, but may reveal changes in residence not documented elsewhere.

For larger or recently modified properties, consider tracking down current or former maids, plumbers, electricians or other tradespeople with significant knowledge of the inside of a building. Direct interrogation of such witnesses is likely to filter back to current residents.

Serious and qualified “ghost hunters” are rare. Immediate neighbors are more reliable. It is also helpful to contact local scientific skeptics. Right or wrong, they will have plausible-sounding dismissals on hand.

How do I establish cover?

Getting inside an occupied building without drawing suspicion usually requires a long-term operation, becoming neighbors, tutors, handymen or organizers of a local church group with an interest in exorcism. Even with time, this is rarely practical, as these forms of cover will generally not allow for a thorough investigation.

Shallow cover is usually sufficient to assess the likelihood of paranormal activity. Consider posing as police officers acting on a tip, fire safety inspectors, asbestos-removal entrepreneurs offering a free survey, etc. The most effective cover is usually that of private paranormal investigators or psychics, assuming the residents are not implicated and defensive.

Upper-class homes victimized by paranormal activity or unexplained deaths are likely to require new domestic staff, but even such a secure position inside is difficult to leverage if evidence is not plain to see. A thorough investigation of a house requires unrestricted access to the property for at least a week, which could be the residents' regular vacation. Commercial and industrial properties are even more problematic, but more easily infiltrated under cover of employment, or investigated by night.

What am I looking for on a first visit?

Bring a good camera, and a macro lens. In urban areas, almost every public assertion of paranormal activity is accompanied by the reservation that the activity in question is intermittent, unpredictable and undetectable in daytime. This doesn't always mean the claim is phoney. High-resolution photographs establish the baseline of future observations, and should be taken in quantity before you start moving the furniture.

The main use of a floor plan is to spot divergence from it. Minor modifications can hide larger ones. Look for rooms that are too short, furniture that may conceal doors just large enough to crawl through, thick carpets or loose floor boards covering hatches. This serves to rule out the simplest explanations, but has a second purpose. Structures and materials of no practical value may be an attempt at efficacious geometry, and will often be hidden.

How do I conduct a more thorough investigation?

Place microphones and low-light surveillance cameras. If you find nothing in the region of visible light, work your way out. Beware of human artifacts from wireless communication. Equipment to visualize further regions of the electromagnetic spectrum can be procured if the initial assessment justifies it, but do not neglect your other senses, or extensions thereof.

Visit in the night, to listen. Feel for vibrations too slow or too fast to hear. Before trying to smell something, take in a deep breath of fresh air to minimize exposure of your internal tissues. Be prepared for anomalous temperatures and static electrical charges.

Peculiar substances should be run by a Friendly analytical chemist before you consider tasting them. Otherwise, remove nothing from the location. Use two layers of gloves, and be wary of molds and mites until you've seen them in close-up. In the event of medical symptoms arising in a search, request Friendly medical attention and quarantine yourself at the location for at least 48 hours, especially if there is no help coming.

The sense of balance is too often neglected. If you feel disoriented, crouch down and dangle a small weight from a dynamometer to determine the stability and acceleration of gravity, including its direction. If gravity matches the geoid, the likely cause of your disorientation is an optical illusion, generally caused by a slanted horizon or subtly irregular architecture.

If the activity appears connected to an elusive biological entity, consider knocking down non-load-bearing walls with appropriate safety equipment, including respirators, face masks, safety goggles and ear plugs. In idle moments, rehearse your path to the nearest exit.

What if I find something?

Concluding an investigation is harder than it looks. A gas leak, while easily explained, is not reliable. Dynamite is appropriate for concrete, but rarely adequate for thick steel beams. Familiarize yourself with the equipment by practicing the entire process in an uninhabited area. At the actual site, you will rarely have time to verify that all of the explosives ignited.

Clear all access ways, and evacuate the public to a safe distance, typically 1000-2000 feet. Soften the central supporting columns before placing the explosives inside them, and on the evidence. Set the charges so that each section topples away from the building's center, unless dense urban surroundings require an implosion.