I'm Lester Holt, tonight on Dateline. Her disappearance made headlines across the country,

the mom who vanished on Thanksgiving Day.

That video snowballed into this big mystery, and your family is like right in the middle of it.

Kelsi would never, ever have abandoned her baby. Never.

I'm trying to find a missing person. The supervisor asked me to interview a girl named Crystal.

We didn't really have any idea who she was.

One all over the floor, and I'll go up the wall.

She told us everything.

When she started being cut first, I started picking up things that were blood splatters.

This woman, knew about a murder, covered it up, the things that were thrown into the fire by me,

or the belongings from Kelsi's house.

She could have stopped this from happening.

He had a hold on her that he totally exploded.

This whole thing is crazy.

Took my breath away.

Here's Andrea Canning with Devil's Bargain.

Was there any blood on the TV you ever know? Yeah, there was blood on the TV.

There was blood on the chairs. There was blood on the chairs. There was blood on the table.

There was blood on the hobby. We'll all be mad that we're sitting there.

You're witnessing something highly unusual.

A woman at the center of a murder investigation reconstructing the scene of the gruesome crime.

Can you tell me what you saw in here and what you cleaned up?

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