If you believe your house is haunted, or want to try some investigating yourself, the online directory paranormalsocieties.com lists some 30 groups in Maryland that offer their services, usually free of charge. Here are a few operating out of the Baltimore area.

Group: Greater Maryland Paranormal Society

Founded: 2006

Investigators: 13

Location: Curtis Bay

Website: greater-maryland-paranormal-society.com

Caseload: 16-25 investigations a year

"I grew up in a house in Brooklyn that had paranormal activity," says founder and lead investigator Bill Hartley. "I spent most of my childhood and teenage years thinking there was something wrong with me. Then I found out that a guy had committed suicide in the house. That kind of vindicated what I was seeing. When I approached my mom and told her, she was like, 'Good, you see him, too.'"

Group: Inspired Ghost Tracking

Founded: 2008

Investigators: 8

Location: Odenton

Website: meetup.com/inspiredghosttracking

Caseload: About 15 investigations a year

"I never tell anybody, yes, your home is haunted," says founder/organizer Margaret Ehrlich. "Who gives anybody the right to do that? We give them the evidence that we come up with. I let them know what we found, what we didn't find. If you want to call your house haunted, that is up to you."

Group: Spiritus

Founded: 2006

Investigators: 10

Location: Catonsville

Website: spiritusparanormal.com

Caseload: About 10 investigations a year

"We actually have skeptics in our group," says co-founder Don Godman. "We've had our own experiences, so we know that paranormal activities exist. We really don't spend much time trying to convince people there's activity out there. People are either going to believe or they're not."

Chris Kaltenbach