When my Aunt Reet was staying at an inn in Gettysburg, she woke up in the middle of the night to the sound of someone trying to get into her room. When she opened the door to see who it was, she saw a man walking away in what looked like an old, threadbare Civil War uniform. At the end of the hallway, he turned toward where the bathroom was and disappeared.

She went back to bed, and each time she was drifting off to sleep, a mischievous presence would tweak a lock of her hair and wake her up. My cousin, whose idea it had been to stay in the haunted inn in the first place, was upset that the ghost had appeared to my aunt and not to her.

I don't have much desire, or apparently ability, to see ghostly spirits, but I am fascinated by the topic and collect all the stories I can. As a guide for Philadelphia's Grim Philly Twilight Tours, I had the opportunity to attend a few ghost-hunting events run by the owner, Joe Wojie, a Rider University history professor, and Laurie Hull, a paranormal investigator from Tri County Paranormal.

I'd grilled Laurie while we were planning the event, so I knew that ghosts had an unhealthy attachment to a job, a place, or a person on earth that prevented them from moving on, while spirits had passed over but could come back to check on loved ones, which was healthy. She maintained that anyone could learn to see ghosts, but some people had more of a natural affinity for it than others. Ghosts reach out, she said, for the most part, because they simply want someone to listen to their stories.

During Grim Philly's ghost hunt, participants used EMF meters to measure disruptions in the electromagnetic field that paranormal investigators believe are caused by spirits. We registered electromagnetic activity near the site of Dr. Benjamin Rush's house, which is said to be haunted by the ghosts of yellow fever victims. The meters were also active around City Tavern, rumored to be haunted by a bridal party that burned to death and a man who was killed in a bar fight there.

As I trailed the group, my meter blinked red all the way from the Robert Morris statue to the site of Surgeon's Hall. The area is supposedly surrounded by the ghosts of cadavers robbed from graves in Washington Square. When the eerie sensation that a presence was walking right along with me got to be too much, I ran back to the group. When I told Laurie, she wasn't surprised. Apparently ghosts are curious about what the group is doing and follow behind.

Estimates of the number of dead bodies buried at Washington Square range from 4,300 to 7,500. The square served as a "potter's field" for the dead of the poor, as a burial ground for American soldiers executed during the Revolutionary War, and as a site for mass graves of yellow fever victims. Laurie says the message she gets from spirits there is that they want people to know it's a cemetery, not a park. Most of the people who walk through the square have no idea that they are walking on a burial ground.

At Washington Square, one of the participants videotaped balls of light bouncing and swirling around her friend. She said she felt very cold and out of breath during the experience. Laurie thought the balls of light were souls. When we pulled out the dowsing rods, L-shaped rods made of lightweight metal that cross in answer to questions, they would only point at one participant, Jake (who had been getting the best readings all night), and at Laurie as the most sympathetic members of the group. I held the rods and turned my back toward Jake, but the rods still whipped around to my shoulders to point to him. It was uncanny.

Perhaps there is another reality coexisting with ours, overlapping and intersecting our layers, fraught with feelings not unlike our own. Maybe allowing a ghostly spirit or two to make connections will help them rest in peace.