In The Doomsday Mother: Lori Vallow, Chad Daybell, and the End of an American Family (St. Martin’s, Jan.), crime writer Glatt probes a horrific case of child murder.

Why have you called this the most “terrifying” case you’ve encountered?

Out of the 25 true crime books I’ve written, nothing really compares to the evil that Lori Vallow committed in allegedly killing her children, Tylee and J.J., and her and Chad Daybell’s respective spouses in cold blood. Just to see the body-cam video of Lori cracking jokes to police less than an hour after her brother Alex shot her husband Charles Vallow to death was unnerving.

What was the hardest part of writing it?

Trying to get my head around Chad’s highly detailed, but demented, light and dark readings of everyone. His blasphemous version of the Mormon religion played such an important part, so I had to research the Mormon theology, which I knew nothing about beforehand. It was harder than my other books because it was amazing to me that they could get away with so many suspicious killings and disappearances for so long. It surprised me that they literally had a legion of followers all over the country who believed everything they told them, however bizarre.

How do you explain Chad’s delusions?

I think Chad loved the idea of being an author/publisher and it fed his ego, and made him feel important. He was writing books about the end-times for years before this, and, after moving to Idaho and doing podcasts and public lectures, I think he lost his grip on reality.

Were there missed opportunities to save the children’s lives?

Absolutely—many of Lori’s friends were suspicious, and could have gone to the police earlier after J.J. and Tylee disappeared. I think there are lessons to be learned from Chad’s cult, which flourished in the open for so long. Law enforcement should monitor any suspicious cult activity far more closely. This case clearly shows how people should report strange, cultish behavior to law enforcement and not keep it to themselves.

Do you see any connection between Lori’s delusions and the current prevalence of misinformation?

I think Chad and Lori’s delusions about people being transformed into evil zombies is a perfect example of what is going on now with truth and reality. I compare it to George Orwell’s doublethink in 1984. I think the growth of social media and podcasts made it possible for Chad and Lori to spread their madness to a far bigger audience than would have been available 10 years ago.