(NBC News) — Tonight on “Dateline” — new evidence, secret recordings and exclusive new interviews — all part of the Lori Vallow and Chad Daybell saga.

Here’s a preview of Keith Morrison’s report:

We’ve been reporting on this story for almost two years now.

And tonight, there’s new evidence. The most complete picture yet. And revelations.

Interviews with Lori and her daughter, Tylee.

And Alex, Lori’s brother, and alleged hitman.

New text messages, recordings, interviews, crime scene photos.

New details about the adulterous affair that set the whole terrible sequence in motion.

A crime wave that moved so quickly, police in three states could not keep up with it.

There is also new evidence about what happened to the children and about other children who may have had a close call.

Much of the story we’re going to tell you tonight comes from files that have only recently been made public— new evidence— the puzzle pieces of this strange tale, wild and deadly, which grew, perversely from an occasion devoted to piety.

On Friday’s “Dateline,” the brothers of Lori’s ex-husband, Charles, are speaking out for the first time.

Watch “The Doomsday Files,” tonight on NBC4 at 9 p.m.

About “Dateline”

“Dateline NBC” is the longest-running series in NBC primetime history and is in its 30th season. Dateline is anchored by Lester Holt and features correspondents Andrea Canning, Josh Mankiewicz, Natalie Morales, Keith Morrison and Dennis Murphy.

Dateline is the #1 Friday newsmagazine and reaches more than 17 million people every week through its broadcast, and millions more through its social media platforms and podcasts.

The stories range from compelling mysteries to powerful documentaries and in-depth investigations. When major news breaks, they go to the scene, putting the pieces together to bring the viewer the full picture. And in every story they tell, they help the real people who lived the events share their journeys with the viewer.

This past season, Dateline debuted two new podcasts, “Mommy Doomsday” and “Killer Role,” hosted by correspondent Keith Morrison.

In February, NBC also greenlit a straight-to-series inspired by the story featured in the Dateline podcast series, “The Thing About Pam.” Two-time Oscar-winning actress Renee Zellweger will star and executive produce the series, in collaboration with Blumhouse Television, NBC News Studios and Zellweger’s Big Picture Co.