Fighting Satan’s minions wasn’t part of Gallagher’s career plan while he was studying medicine at Yale. He knew about biblical accounts of demonic possession but thought they were an ancient culture’s attempt to grapple with mental disorders like epilepsy. He proudly calls himself a “man of science.”

Yet today, Gallagher has become something else: the go-to guy for a sprawling network of exorcists in the United States. He says demonic possession is real. He’s seen the evidence: victims suddenly speaking perfect Latin; sacred objects flying off shelves; people displaying “hidden knowledge” or secrets about people that they could not have possibly have known.

“There was one woman who was like 90 pounds soaking wet. She threw a Lutheran deacon who was about 200 pounds across the room,” he says. “That’s not psychiatry. That’s beyond psychiatry.”