Keith Morrison Correspondent • Profile

NASHVILLE - Love can be so unpredictable. Gentle, caring.

Or it can also be a passionate fire, out of control, scorching what it touches, and consuming the lives of the lovers pulled back for more.

Such was the romance, and its fate, at the heart of our story. It’s a story told, in part, through a raw and shocking videotape which captures the most private of moments. Two lovers on a long weekend that would end in death.

Tara Bentley: They loved each other as much as they seemed to hate each other. As much as they loved to argue.

Tara is talking about the toxic love affair which had consumed her sister, the head-turning Lesa Buchanan, 35. They had grown up together, Lesa the younger of the two, in Dayton, Ohio.

Tara Bentley: One of the memories I have of her is just she was always wanting to fight for the underdog and fight for the people that she cared about.

Lesa married and had a daughter named Jessie, but wanted more.

She began modeling, often for a Cincinnati photographer named Gary Kessler.

Gary Kessler: Lesa was great. She was very vivacious and bubbly and full of life.

And she had big plans.

Gary Kessler: Lesa wanted to write movies and star in movies and she created a script. Lesa just had a lot of hopes for the future.

And so she divorced her husband and left Jessie with her ex, while she set out to conquer Hollywood.

After enduring a succession of odd jobs and rejections, Lesa headed for the center of another kind of fame. She went to Nashville.

And that's where Lesa was in January, 2000.

It’s odd, that a woman so young, so lovely, would be attracted by a plastic surgeon's ad for a free consultation.

Christ Koulis: She was very vivacious. She was alive. She had a great sense of humor.

The doctor’s name is Christ Koulis [pronounced like “Chris”].

Koulis was, to all appearances, quite a catch. He'd breezed through medical school in Nashville, set up a very successful practice there. Though his first encounter with Lesa was professional, it certainly didn't stay that way for long..

Keith Morrison, Dateline NBC: What'd she say about him?

Tara Bentley: She met this great guy, of course, and he was a doctor. And she was happy.

And the money? Well, that was no small thing to Lesa.

Gary Kessler: Lesa was always looking for someone who could further her career.

But as anybody close to her could see, Lesa was truly in love, or certainly seemed to be.

Tara Bentley: I think Christ could absolutely be very charming. He absolutely could. He was very knowledgeable. Very intelligent.

They were a very handsome couple. He moved her into a lovely Nashville home, where they soon discovered that they were nitro and glycerin when together.

Tara Bentley: It became pretty normal from that point on for there to be fighting and then a gift and fighting and making up.

There was that time, Tara remembers, when she and her mother took Lesa away for a few days of girl time. And the phone never stopped ringing.

Tara Bentley: I finally just grabbed the phone and told him that he was ruining my vacation. And he had to leave her -- he had to stop calling.

Of course, Lesa was constantly checking up on him, too.

Tara Bentley: She called him. He called her. And I think that over time it became a two-way street.

According to her sister, there was good reason for Lesa to keep tabs on her boyfriend.

Tara Bentley: I absolutely remember instances when Lesa would find e-mails. Or she would find ads that Christ had put online on dating sites. She knew that he wasn't faithful and yet, somehow, she still was drawn to him.

By summer, 2005, Koulis had moved to Chicago. Lesa was embarking on a career as a children's book writer and puppeteer. Since her return from Hollywood, she had been sharing custody of her daughter with her ex. Now Lesa took Jessie back and the two moved to Franklin, a charming old town outside of Nashville.

Morrison: Your chemical attraction to each other was really the only thing that you had at that point?

Christ Koulis: That was part of it. And there were still remnants of a relationship where we cared about each other.

It was the July 4 weekend, 2005, when it happened.

Lesa complained of a headache.

Christ flew down from Chicago to spend the weekend.

On the morning of July 4, he was in the kitchen, getting breakfast, when Lesa called him to the bedroom.

Christ Koulis: And I sat down next down to her. And I put my hand next to her over here on her cheek. Said, "Honey, what's wrong?" And she just stopped all of the sudden.

Morrison: Stopped?

Christ Koulis: Her eyes became fixated. You could tell that something was wrong and she rolled back. Her lips turned pur – she -- I realized she wasn't breathing. My god. And I slapped her. Maybe not the best medical thing to do. But, I mean, you know, "Honey, what's wrong?" she wouldn't respond. I felt for a pulse. Lesa was not breathing.

He called 911.

911 operator: Sir, what's going on in 1705 Cold Springs?

Koulis: Well, she just stopped breathing.

911 operator: OK.

Koulis: She's blue.

Paramedics did what they could on the way to the hospital. ER doctors struggled for almost an hour.

They could do nothing. Lesa died.

She was a young, apparently healthy woman now lying on a slab.

Christ Koulis: I keep asking that question to the ER doctor. Why? I don't get it.

Soon that question, “Why?” was contagious. Nobody got it. A detective came snooping around and very quickly decided that Christ Koulis was giving answers that did not add up.

Eric Anderson: The things that were found at the apartment were strange. His information was strange. The facts of the matter were strange. Everything about it was very odd. It raised a lot of red flags with us as investigators.

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