A few hours before our Sunday evening service, I received an urgent call from a staff member: "We need you here! We've got a young woman here with her fiancé … and she's convulsing … it's spiritual stuff!"

I advised him to call 911 and said I'd be right over.

Ten minutes later, I walked into the foyer of our church's building. A small group of people stood near a young woman seated in a chair. Some of them were praying, a few with hands on her shoulders. I watched her body repeatedly stiffen and relax.

Maybe this is a seizure, I thought, but maybe not …

I sensed something unnatural in the room. The entire foyer felt filled with a dark and oppressive presence.

Since an ambulance crew hadn't shown up, I was pretty sure no one had called 911. Later I would learn that the young woman and her fiancé had gone to a local hospital and a few other churches earlier that day but were unable to get help.

I sighed and walked toward the ...