A beloved mail-carrier. A house on fire. And a smoldering mystery consuming a devastated family.

The family's grief explodes into anger as they try to get to the bottom of a mysterious fire. Crime Watch Daily pieces together the clues of what really happened to Laurie Merritt.

Wilkes-Barre, Pennsylvania is a big city with a small-town feel.

"The houses are fairly close together. I don't think a lot happens in this neighborhood without other people noticing," said WNEP-TV Reporter Sarah Buynovsky.

And nobody knew the neighborhood better than Laurie Merritt, a vivacious mail carrier whose route was as much pleasure as business.

"Everybody loved her," said Joe Walkowiak. "If somebody was sick on her mail route, she would take them food, take them whatever just to comfort them. Laurie wanted everybody to be happy."

But there was one home on her route that wasn't happy -- the one Laurie shared with her longtime live-in boyfriend, Paul Kosakowski.

"From day one, nobody liked him. Not my grandparents, not my aunts and uncles, not her friends," said Kristin Merritt. "He was very controlling. He didn't want her to have any guy friends. He was super jealous."

After 17 years of bickering and breakups with Paul, Laurie calls it quits for good.

"She told me she was finally going to start living her life and not worrying about what she does, not caring about what he thought of her now," said Jeff Walkowiak.

But for months after the breakup, Laurie's brother Joe says, Paul couldn't let Laurie go.

"She said that she would come home and she would find Paul looking in the windows, he'd be around her house stalking her, and that's when I said 'Laurie, something's not right here,'" said Joe.

And then, Joe says, Laurie had enough of the drama and drops this chilling aside:

"One day she came to me and she said 'Listen, I'm done, I don't care,'" said Joe. "She said 'If I'm dead, Paul killed me.'"

April 14, 2014 was a Monday much like any other. Laurie works her route delivering the mail, makes dinner, faxes her taxes and makes several phone calls, including one to her good friend Ken Huhn.

"We were talking about food and things like that, and she was actually in the process of getting me a recipe," said Huhn. "And she said 'I'll call you tomorrow with the recipe' as if it was nothing."

But sadly for Laurie, tomorrow would never come.

That night a neighbor notices smoke coming through the roof of Laurie's house.

"My grandmother called me and she said 'Your house is on fire,' and I'm like 'Where is my mom?' She said 'We don't know,'" said Kristin Merritt. "Everybody is calling her, no answer."

Firefighters desperately search the house for Laurie, but she's nowhere in sight. Then they pull down the steps to the attic. Inside the cramped space they find a small 4-by-4 patch of smoldering flames. And horror. Laurie is lying face up, her phone by her side, her lungs full of smoke and soot -- still alive, but barely.

"They said 'You need to go to the hospital. It's not good,'" said Laurie's daughter Kristin.

Tragically there's nothing doctors can do.

"She was pronounced dead a short time later of carbon-monoxide poisoning and smoke inhalation," said reporter Sarah Buynovsky.

Laurie Merritt's family is overcome by grief.

"We were a close-knit family. And after she passed, all that kind of went away," said Jeff Walkowiak.

But through their tears, her family says something about Laurie's death doesn't look right. Their first question: Why didn't firefighters look for Laurie in the attic on their initial search?

"The reason they didn't go up into the attic is because there was no steps there," said Joe Walkowiak.

Jeff and Kristin showed us the process of getting in and out of the attic. It's not easy. In fact, the first part of the ladder leading to the attic is detached. They're actually leaning up against the kitchen door.

"[Firefighters] told me that they walked in the house, searched the house three times. And I said to them, 'Are you sure those steps were not down?' They said 'Absolutely,'" said Joe.

That's strange, Kristin says, because it would be impossible for Laurie to disassemble the bottom half of the ladder, set those steps against the kitchen door, then climb back up by herself and get trapped in the attic.

"It's almost impossible to get those stairs down once you're in the attic, so she wasn't alone," said Kristin.

And the family's alarm bells go off when the state's fire marshal issues his report.

"He determined that it was arson, that there was combustible material in the attic space that had been lit by someone," said Sarah Buynovsky.

The fire is declared an arson, and Laurie Merritt's cause of death is changed.

"At that point the coroner's report which was initially that this was an accidental death changed to 'undetermined,'" said Sara.

"Somebody started that fire," said Joe.

But is it possible that somebody was Laurie herself?

"She did smoke cigarettes, yes," said Jeff Walkowiak. "She would not let you smoke in her house. She always came out here on the porch."

"The cigarettes that she did smoke, the state police fire marshal did a test on it and put it in a pile of hay and did all kinds of tests and couldn't start a fire. That cigarette couldn't start a fire," said Joe Walkowiak.

To Laurie's family, it's just not adding up. So they do some digging and theorizing on their own. Authorities aren't commenting on this open case, so we can't verify their claims.

The night of the fire, Joe searched Laurie's house, looking for anything to explain what happened to his sister.

"I did my own investigation. I went into her bedroom," said Joe.

It's there that Joe claims he finds something that sends chills down his spine.

"She had a gun permit filled out, ready to go," said Joe. "So she was afraid. She was in fear of something."

And Joe says he knows exactly who Laurie feared: Her ex-boyfriend Paul Kosakowski.

"That's how he controlled her, is by fear," said Joe.

Reporter SarahBuynovsky has covered the story for Crime Watch Daily Wilkes-Barre affiliate WNEP.

"Some of Laurie's family members believe that she was in fear of him, and that their relationship was volatile, and that he was perhaps responsible for some of her emotional turmoil, or created issues with her, created fights with her, and problems," said Sarah Buynovsky.

Laurie's family says it's more than "emotional turmoil." They say Paul refused to let Laurie go and that led to some odd behavior, including a text from Paul to Kristin.

"It was from Paul, and he tells me that to prove that he's been spending time with my mother behind my back, he planted notes in my house and told me where they were supposed to be hidden," said Kristin Merritt. "We found at least a half a dozen notes. In one of them he wrote, 'Hi Kris.' I felt like they were targeted at me, like he was trying to drive me and my mother apart.

"So I just told him he was pathetic and left it at that," said Kristin. "I wasn't going to give him a reaction. He was just so obsessed with her. Normal people don't go planting notes in somebody's house for their daughter to find. It's really strange."

But Paul Kosakowski insists to cops he was nowhere near Laurie Merritt's house at the time of the fire.

"I believe it's that he was at home with his mother, sleeping. That's what he told the police," said Kristin.

Paul Kosakowski has never officially been a suspect or even a person of interest in the case.

But there's one more phone conversation Kristin says that puts Paul's alibi into question: the call Laurie had that night with her friend Ken Huhn.

"It was a normal conversation until the end, and what she said was 'Oh, Paul's coming home, I gotta go,'" Ken tells Crime Watch Daily.

Laurie's family takes all their evidence and allegations to police.

"I told them everything I knew, and they scribbled down on a little notepad. I had notes, I had evidence, and they didn't take it seriously. They didn't even keep what I gave them," said Kristin.

Both the Wilkes-Barre Police and Luzerne County District Attorney declined Crime Watch Daily's requests for an interview, saying they are "currently awaiting some information before any comment would be able to be made."

There's one person the family thinks can answer all their questions. But after 17 years in their lives, they say now Paul Kosakowski is making himself scarce. Kristin tells Crime Watch Daily that Paul didn't come to the hospital, and didn't reach out to her or anyone in the family.

Laurie's heartbroken family wants to know why.

Laurie Merritt's family says they believe they know who killed the 51-year-old mail-carrier, but they aren't sure they will ever get justice.

Laurie's daughter Kristin and brother Joe are convinced Laurie was murdered, killed in a fire they say someone intentionally set. Kristen and Joe have deep suspicions about Laurie's ex-boyfriend Paul Kosakowski, and they refuse to remain quiet.

"He was just so obsessed with her," said Kristin.

Joe alleges that Paul's obsession turned to furious rage when he saw flirtatious pictures from other men on Laurie's phone, one of them sent that very night.

"And half an hour before she died, she sent him a cartoon of 'He can't wait to see her,' with a cartoon picture on it and whoever was there, whether it be Paul or somebody else, saw that picture, and I think that's what started the fight," said Joe Walkowiak.

But was that fight with Paul? Ever since that horrible night in April 2014, Joe and Kristin say they haven't heard one word from Laurie's ex of 17 years.

So Crime Watch Daily reached out to Paul Kosakowski to get his side of the story and to figure out what happened to try to hopefully give Laurie's family some answers.

"I think the victim of the fire, OK, was the person who lit the fire," Paul told Crime Watch Daily. "I do. I hope it was an accident."

Did you have anything to do with her death?

"Absolutely not," said Paul. "Absolutely not. I told the investigators that. They gave me a voice polygraph, OK. I had no fear of it whatsoever."

As for that night, did you go to the house at all?

"I was not at the house. I wasn't even in the neighborhood," said Paul.

After telling us he is completely innocent, Paul makes a shocking claim, saying Laurie wasn't upset with him -- but she was livid with her own daughter, Kristin.

"Oh, she was very upset over her daughter. She was very upset over her daughter," said Paul. "Well, she left a note for her, she told me, and she said 'I left her a note, and she did not do a damn thing I asked her to do. Nothing.' She said 'That kid doesn't help me, she does absolutely nothing for me.'"

And those notes Paul left for Kristin to find? There's a reason for those.

"Because Laurie was telling the daughter the direct opposite," said Paul. "I had heard that [Laurie] hitting the bar scene and seeing somebody, and you know, the brother-in-law told me like, 'Oh, stay away from Laurie, you know, she's been with somebody else now.' Didn't matter, I loved Laurie very much. Absolutely I miss her, every single day. You have no idea."

So why has he cut off contact? Paul says he's gone out of his way to avoid the family drama, and did not go to the funeral.

"Why, why should I make a bad situation even worse being there? Her family told me that night when they called, you know. They said 'What did you do? What happened? What did you do?'" said Paul. "They have to stop blaming me. Stop blaming me. I did not harm Laurie. I did not."

"I don't believe a word he says," said Joe Walkowiak. "Paul should be given a lie-detector test. Paul did not take a lie-detector. He took a voice-stress test, which is a bull test."

"We just want the truth, that's it," said Kristin. "All we want is the truth."

Investigators' latest hope? The truth may come from the iPhone found at Laurie's side in that smoldering attic.

"They obtained a computer program that did unlock the phone, but we've not learned what's on that phone," said reporter Sarah Buynovsky. "They'll keep it close to the vest until there's something to share."

Until any new answers come to light, Laurie is never far from this heartbroken family's thoughts. And nothing will break her daughter's relentless fight for justice.

"I'm not giving up, no matter what," said Kristin Merritt. "I know somebody did it and somebody deserves to go to jail for that."

Kristin says the only thing that helped her get through the loss of her mom was the birth of her own daughter, who was due exactly nine months from the day her mother passed away.