A brilliant young architect mysteriously died just before she testified in a criminal trial.

Her diary contains stories of sex, betrayal, and intrigue.

Investigators needed to know if the stories were true.

Music to know if the stories were true. University Park, Texas, just outside of Dallas, is better known as the bubble.

It's a place of privilege and prestige,

an address many would like to have,

but few can afford.

It's kind of the Beverly Hills of Dallas.

That's the way the Park City says.

Nancy Dillard Lyon lived most of her life in Texas.

She was a Harvard-trained architect

and the daughter of a wealthy and well-connected Dallas family.

Nancy met her husband Richard while at Harvard.

They married and soon had two children.

They had great energy, great friendliness. When we moved in, they gave gifts of ice cream, and they baked cookies and bring them over to us.

And my husband, who I've said is rarely hyperbolic about anything, used to say she was the nicest person in the world.

Nancy quickly became the youngest partner in the history of Trammold Crow, a large real estate development firm.

But success came at a price.

I think she always had, as many women did at that time, a conflict between the amount of hours that she wanted to work to develop her career and time spending with her children.

Nancy was also experiencing some physical ailments. And on a January night in 1991, her symptoms

included vomiting and severe stomach pain. Her husband Richard took her to the hospital emergency room.

Doctors were initially baffled.

...