question. Is a killer still walking the streets of the small American town, because tonight, authorities say where there's smoke, there's fire. And not just a house on fire, but a burning bed. Tonight... See More
question. Is a killer still walking the streets of the small American town, because tonight, authorities say where there's smoke, there's fire. And not just a house on fire, but a burning bed. Tonight here who was in that bed and was the kill earl one of them? You're about to get an inside look at the evidence. You decide. Here's Jim Avila. Reporter: 3:00 in the morning down hidden meadow court. A warm, sticky night, clear skies, full moon, the peaceful scene shattered by a spark. Gaston county 911. We have a house fire, fully engulfed, 4835 hidden meadow court. You think there's somebody inside? Reporter: Suddenly the sky lights up bright. A house is burning, and it looks bad. Neighbors are horrified. We think there is somebody inside, please help us. There's a lady's car here, she's not answering -- there's no way she's going to survive this. And now at noon, a house burned down to the ground where a mother and two children lived. Eyewitness news reporter ken lemon, he's been on the scene all morning. Reporter: Reporter ken lemon is among the first on the scene. As you mentioned, police can't stay it was that woman. The house was in ruins. And you could tell it was a pretty bad fire. Reporter: The missing lady is 31-year-old Lucy Johnson. Married twice. A well-liked young mother living with her two children, working as an emergency room nurse. Lucy's children are safe. They had spent the night with their respective fathers. But where is Lucy? And then I hear from more neighbors who say, you know, "I was at the back door. I was at the door trying to get in and I couldn't get inside." And they began to tell me about the woman they couldn't account for. Reporter: This grim document obtained from the investigation file has the terrible answer. It shows a badly burned body in an upstairs bedroom. As you know, we do have a body in the house and it is deceased. Reporter: That body, unrecognizable, identified only by dental x-rays and the serial Numbers on her breast implants. And sadly, yes, it is Lucy. A police officer calls her father, Mike dye. She informed me that there was a fire at Lucy's house, and I asked her, I said, "Well, did Lucy get out?" She said, "No, Lucy is still in the house." So, I broke down. Reporter: With a body inside, this is more than a fire. Police are called, arson inspectors. It's an all out investigation. In the ashes, those investigators immediately notice something strange -- the burn patterns. A trained fire dog detects a suspicious trail of burnt gasoline leading from Lucy's bed, down the blackened stairway and out the back door. It wasn't an accident. Reporter: No, this is arson. And then suddenly this car comes racing right up to the police tape. And this guy jumps out and he runs into the arms of the first person there and he starts crying. Reporter: It's Mike mead, and he's trying because inside the smoking hulk of a building is the woman with whom he's planning a future. When you get there, what do you see? Oh, lord. The house was still smoldering, still smoking. Reporter: Lucy was his fiance. You think to this day that she was the love of your life? Yeah, I think she was. Reporter: Mike mead and Lucy Johnson were building that future in Gaston county, north Carolina. Once known for cotton mills and corn whiskey. West of Charlotte, maybe, south of justice. Where authorities now have to ask -- who would want to burn Lucy's house down? Friends and family say Lucy was on the feisty side of southern belle, a good woman with a weakness for cigarettes, mountain dew, pick-up trucks and the men who drove them. Lucy's uncle, ken dye, likes to call some of them unsuitable gentlemen. She had problems with men. Reporter: Bad choices? Bad choices. Reporter: Deana Bradshaw has known Lucy since they were teenagers. She needed love. She never wanted to be by herself. And I believe that was her downfall. Reporter: Lucy likes kids. Shell has a 7-year-old daughter with her first husband and a 6-month-old infant son with a recent ex-boyfriend, a man named Jim spelock, who made his living at the nearby kacatawba nuclear plant. Now, lately there is little love lost between Lucy and Jim. Broken up before their baby is even born. In fact, after the delivery, right there in the recovery room there is a nasty scene over, of all things, the newborn baby's name. I have never seen an individual so obsessed with the naming of a child. Reporter: Private investigator Steve Ehlers says spelock wants the baby named after him, James spelock iii. But headstrong Lucy would have none of that and names the boy Cason. That doesn't go over well with daddy. They arguey nd luckicks Jim out of the maternity ward. And he doesn't go quietly. Taking with him baby presents and the car seat. He just went into a berserk outrage. Takes her car and leaves her stranded at the hospital with no way home, no car seat. Reporter: Jim and Lucy spend a loft time in and out of court, fighting over custody, child support and that name. Yeah, if she wanted to get her way, she was going to get her way. That was Lucy. Reporter: She was outspoken. Yes. She didn't take no stuff. Reporter: But by the summer, some daylight begins to shine on Lucy's life. That's when she meets, online, 39-year-old Mike mead. He has a pickup, phew he also has a BMW. A successful inventor and entrepreneur from nearby fort mill, South Carolina, who enjoys the finer things, like sitdown dinners at the steakhouse chain. She was dressed really nice. I dressed up nice and we went out to longhorn, had dinner. You know, I was real curious about why she was wanting to date somebody when she just had a baby. Reporter: Can I ask you what was special about this relationship? How you get that attached that soon? I just felt like we really had this connection, and we went right into family mode. The kids all got along, our three dogs got along, I mean, it was like just everything just clicked. Reporter: They hit it off. Whirlwind relationship. And right off the bat, less than three weeks after meeting, Lucy has some news for Mike -- she is pregnant. Very unexpected, very unplanned. Reporter: You just met this woman. Right. Reporter: And soon after you find out she's going to have your baby? That's right. Reporter: Mike says he quickly got used to the idea of becoming a new dad. They were in love. Mike saved this voicemail Lucy left two nights before her sudden death. Hey, baby, it's me. Just calling to say good night. I'm going to bed right now. So, I love you and I'll talk to you tomorrow. Bye. I was happy. I was tickled to death, you know. Lucy was beautiful, smart, she was a fantastic mother. You know, I couldn't think of anybody I'd want to have a baby with more. Reporter: So tickled that just three months into their love affair, he gives Lucy a diamond engagement ring. A great big one. We felt like, you know, we're going to be together, we're going to have this baby, it's going to be wonderful, so you know, let's just go ahead and get -- let's do it. Reporter: A couple nights later, Lucy cooks Mike a pot roast with biscuits at her home in Gastonia. Good times, says Mike. Until a shadow is cast over the evening by the roar of a pickup truck outside. It's Jim spelock, the ex-boyfriend, arriving for his visitation day. There to pick up his infant child for the night. When she came back from the door, her demeanor was all different. Reporter: What did he want from her that night? Well, he told her that he had filed a motion to take Cason to Pennsylvania for two weeks. Reporter: Evening spoiled. So Mike goes home. Lucy drops by her close friend Deana's house to do her hair and show off that ring. It was a very nice ring, large diamond, princess cut, it was a ring that he had previously gave a girl before. He reused the ring and gave it to Lucy. Reporter: Hours later, the spite fire of a young nurse, in love, engaged to a man of means, carrying his child, excited that her life is finally turning around, but now, it's all over. Lucy is dead. Her body sprawled across her burning bed. They said her body was positioned in a funny way on the bed. Reporter: You believe that looked like there was a struggle? Yes. The way it was described. Reporter: Surprisisurprisingly, for a victim of a fire, there is no soot, no ash in her airway. That can mean only one thing -- when the fire started, Lucy wasn't breathing. She was already dead. Suddenly the police clam up. They have more disturbing clues to follow. They still wouldn't tell us anything. They wouldn't even tell us how she died.
This transcript has been automatically generated and may not be 100% accurate.