Zak Bagans, Aaron Goodwin, Jay Wasley and Billy Tolley venture to chilling locales to investigate the presence of some of the most diabolical individuals in history for Ghost Adventures: Serial Killer Spirits. The four-part miniseries is part of Travel Channel’s 31 days of “Ghostober” programming.

“When you hear the backstories on each of these serial killers, your jaws are on the floor,” Tolley said. “Going into it, all of us were already excited to learn more. At the same time, we were shocked, and everyone else will be shocked as well.

First up for the crew is a trip back to the 1800s and Irvington, Indiana. It’s there they visit a Victorian cottage where Herman Webster Mudgett, a.k.a. H.H. Holmes — widely considered to be America’s first serial killer — committed horrible acts, including the murder of young boy Howard Pitezel. Others on the list include John Wayne Gacy, Jake Bird and Ted Bundy.

Helping you mentally prepare for the haunting viewing experience, we sat down with Tolley for further details. You may want to have the lights on for this one.

It seems between movies and TV that we’ve been seen an increased fascination with serial killers. Why do you think that is?

Billy Tolley: Personally, I think people are fascinated by the fact these people can do the things they can do. They are horrific, unimaginable. I think that piques the interest of everybody. Why would someone do that? Why would someone be that way? It causes intrigue.

What is it about H.H. Holmes’ story in the premiere that struck you when you delved into his story?

It was the fact that it was ongoing. There were so many victims. The heartlessness. When you have a hard time grasping someone would do something like that, and with children, no less. Cut up their bodies as if they are not even human beings. The fact we try to communicate not only with the serial killers but with the victims as well. A lot of times that happens. We believe we contact the victims, and if we can, we try to help them. If I feel that there is a spirit trapped, I will do whatever I can within my belief system to try to help them. Whether I’m able to do that or not, there is no way to prove it. There is just a general feeling.

You try to do that in this episode. It appeared you were the most affected by this experience of being in the house. How did this investigation rank in intensity with the others you’ve done?

The fact that some sort of spirit and entity or energy or whatever it might be is able to physically affect you. Whether it’s the sensation of being choked or scratched or hurt or your skin is burning, that will always get your attention. In this episode, whatever it was, the spirit of H.H. Holmes or the evil that caused him to be the way he was lashed out at me because I was trying to help. That occurred more times than not. Evil will try to keep out priests or bishops or anyone trying to help someone that might be trapped. I believe that was the case at H.H. Holmes’ house.

How many times have you finished thinking, “I don’t know if I can do this anymore?”

All the time. First, coming home and clearing myself through meditation or prayer. Each one of us has a method of grounding. For me, it’s my family, my animals, going into nature. It’s kind of putting you back to zero. In the moment, these things happen to you, and you’re at a level 10. Then you realize you’re there for a reason. You’re there to help others. That’s what always brings me back.

You are usually on the AV/tech side. How do you feel advances in technology has helped with your investigations?

I feel it vindicates what we’re doing. The equipment validates what we say we’re feeling more than anything. Everyone has different gifts. I think everyone has psychic abilities on one level or another. Whether it’s a sense of feeling, some people can feel spirits or see. Some can only hear.

For me, it’s a feeling. So when I feel there is spirits around me, and I have a piece of equipment that validates this, it’s great. There are many pieces of equipment we use throughout every investigation. We can see there is something causing the temperature to drop seven degrees instantly, which doesn’t happen normally or an EMF (electromagnetic field) spike that is not a normal occurring thing. I think everyone’s favorite is the SLS (Structured Light Sensor) camera, which produces stick figures. That has happened more than a dozen times and always blows me away, when we sense something and see stick figures showing up. I love that device.

What can you tell us about the episodes to come after the premiere?

Every episode is different. They all have great stories. They all have completely different experiences. We go to the Joliet prison where John Gacy [was incarcerated]. It’s abandoned compared to a house where someone is living. Each of these locations has its own elements that draw you in. The entire miniseries every place we went, it was incredible. People are going to want to tune in to see these stories.

A couple of days ago Zak teased on social media some sort of filming going on in house. What can you tell us about that?

[Laughs] I’m really not at liberty to say and haven’t been given permission to talk about it, other than it’s a new project. And that we’re all really excited about it.

Fair enough. With the miniseries part of Travel Channel’s “Ghostober,” where does Halloween rank in your household? Do you have any family traditions of the holiday?

My kids are grown and over 21, but in the past, we loved Halloween. We used to always decorate the house. It’s the spooky season. What’s great now is that they have their own homes and families and carrying on the tradition of decorating the house. I’m pretty handy, so I do remember about 15 years ago building wooden coffins for props. That is what we kept all the Halloween decorations. So when people came over during the off-season they always asked what was with the coffins. We were really serious about Halloween.

Ghost Adventures: Serial Killer Spirits, Saturdays in October beginning Oct. 5, 9/8c, Travel Channel