I'm Lester Holt tonight on Dateline the dark story that's riveted the country

Mommy doomsday now exclusive new interviews startling new information and a new twist that will leave you cold

We've kept really private but the story had to be told because it's not going away

It's just sick. Who does that to children? Who does that? Did you begin to rethink what happened to Tammy?

Yeah, I did. Who is this woman that replaced my sister? Someone said I have a recording of Laurie Valos saying she wanted to murder your brother

I was going to kill him like the scripture say what he suffered is unimaginable

This is beyond disturbing. What were they planning? What were they concocting?

It was something that could have been prevented.

There's still so much more to come

It's going to be surprising for everybody

Here's Keith Morrison with Molly doomsday

You know her name by now much of the world does

Laurie Valodaybell

She's suspected of some of the worst crimes imaginable

We've been following her story from all that a year

Tractor from the Arizona desert to the mountains of Idaho to the beaches of Kauai

We said nothing

And back to the mainland again

All the way to a courthouse in Rexburg, Idaho

To answer that terrible allegations against her

There's been a clear and alarming pattern in the defendant's life

Of course we know now what happened to her children

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