When Todd Smith went public with the news that his wife Katrina had left their home on the evening of Oct. 22, 2012 and never returned, it sent shockwaves through the couple’s Rockford, Illinois, community.

Katrina Smith was one of their own. Seeing Todd Smith on local TV emotionally pleading for the safe return of his wife resonated with the people of Rockford, and they joined the Smiths’ friends and family in organized searches to locate Katrina. At the same time, The Winnebago County Sheriff’s office was ramping up their investigation into the mystery.

“The way I found out Katrina was missing, was my dad called me, and told me that he hadn't seen her for a while. And I'm like, ‘What do you mean? How long?’” Paige, Todd Smith’s oldest daughter from his first marriage, told “20/20" in her first public remarks about her stepmother's case.

Paige remembers thinking that Katrina would never just up and leave. “I asked a lot of questions to try to understand what was even happening, and my brain at the same time was trying to come up with some sort of rational explanation.”

In the days immediately following Katrina Smith’s disappearance, there was a trail of evidence: her blue Chevy Cruz abandoned on the side of the road in a residential neighborhood was discovered a day after she had gone missing; a day later, her purse was discovered about 150 yards from where her car had been abandoned; the next day her cellphone was found in a bush by the side of the road; the following day a search group found blood-soaked paper towels in a field just south of where Katrina’s car was found.

Her car, her purse, her cellphone, bloody paper towels. But No Katrina Smith.

Watch the all-new "20/20" episode on the Katrina Smith murder airing Friday, Oct. 20, at 9 p.m. ET and streaming the next day on Hulu.

On Nov. 9, seventeen days after Katrina Smith had been reported missing by her husband, her body was discovered in the Rock River by an off-duty firefighter. An autopsy would reveal that Smith had died as a result of blunt force trauma to the head. The missing person case had officially become a homicide investigation.

The revelation raised questions about Todd Smith, and a deep dive into his background led investigators to wonder if his carefully crafted image as the perfect husband, father and successful businessman was all a facade.

For starters, Todd Smith wasn’t always Todd Smith. Smith was once Todd Raprager. In 1985, at the age of 17, he was involved in an incident where he admitted to disconnecting a gas line in the home where he lived with his mother, stepfather and three half-siblings. The home exploded into flames, with Smith’s family inside. Miraculously, the family escaped the blaze without injury.

Todd confessed to the arson, telling investigators he had not been getting along with his mother and wanted to scare her. He waived his right to a jury trial and pleaded guilty to arson. He was sentenced to 30 months’ probation and 160 hours of community service. At just 17 years old Todd left the family home and never went back. Larry Schultz, who investigated the arson case in 1985, told “20/20,” “looking back at it, you’d have to say he was a troubled boy.”

Three years later, Todd met a woman and fell in love. Todd and Teresa were married in Jamaica and the early years were good. In 1992, Todd officially changed his name from Raprager to Smith, putting his past behind him and embracing life as a husband and father.

But Teresa says Todd Smith struggled to provide for his young family. Teresa worked full time and says the burden of supporting their family fell on her.

By the time their third child was born, Teresa says the couple was forced to sell their home to pay off debt and moved in with Teresa’s parents. For Teresa, that was the last straw. Working two jobs and being the primary caretaker for their three daughters was too much and she says she told Todd she wanted a divorce. They separated in 2001 when Todd moved out of Teresa’s parents’ home. They shared custody of their three daughters.

But in October 2001, something happened that has haunted Teresa for more than two decades. Something she has never spoken about publicly, until now.

In an exclusive interview with “20/20,” Teresa recalled the night she was attacked outside her parents’ home in 2001. She is convinced her attacker was trying to kill her.

“I had gone out for the evening… came back home, pulled into the driveway, and I was carrying my keys, my purse, and a Capri sun. I'll never forget that…. and I went around the corner, and I was punched in the face. Full force knocked me off balance.”

The attacker was wearing a werewolf Halloween mask, she said.

Teresa recalled how she found herself on the ground being punched and kicked. She said she was literally fighting for her life. She managed to get to her knees, but the attacker was behind her.

“I know he was going to break my neck. And I just remember thinking that my mom was going to come out in the morning and find me dead in the yard. And when that thought went through my head, I just burst up. I had an adrenaline rush or something. I just stood up really fast and it knocked him backwards. And then I ran.”

A neighbor called 911 and police arrived, asking Teresa if she knew her attacker. Her answer is noted in the police report from that night. The entry reads: “Her husband Todd.”

When asked how she could be sure it was Todd, even 22 years later Teresa is certain. “I mean, I was married to him… I could see his eyes. I could see his body. I mean, it was him.”

Todd told police that he had been home at the time of the attack and Teresa says he denied the allegation when she confronted him about it days later.

Fingernail scrapings taken from Teresa at the scene were compared to fibers on a jacket belonging to Todd, but the results were inconclusive. Teresa also had blood under one of her fingernails after the attack. Detectives wanted to test it for DNA and compare it to Todd, but he refused to cooperate. With no probable cause for a search warrant to obtain his DNA sample, they closed the case.

Now, with early leads on possible suspects in Katrina Smith’s murder quickly drying up, the investigation zeroed in on Todd Smith. Detectives at the Winnebago County Sheriff’s Office were stunned when they learned that at the same time they were investigating Todd Smith for the murder of his wife, the FBI was investigating him for mail and wire fraud related to his alleged role in running a Ponzi scheme.

Teresa had shared the story of the financial struggles that she says plagued her marriage to Todd, but by the time Todd remarried and had settled down with Katrina, he seemed to finally be enjoying financial success. Now police had to wonder if that newfound success was all a façade.

On Oct. 30, 2012, detectives executed a search warrant at Todd Smith’s house. His laptop computer was seized as well as a baseball bat from the garage. Detectives noticed what looked like blood on the bat and it was sent to the crime lab for analysis. In a phone call with the lab on November 21, investigators learned that testing on the baseball bat revealed traces of Katrina Smith’s DNA.

Todd Smith was arrested and charged with four counts of first-degree murder and one count of concealing a homicide. He pleaded not guilty. It would be more than four years before he would stand trial.

While Smith was incarcerated, detectives conducted a second search on a laptop taken from Todd's home in 2012. When police processed Katrina’s car after finding it abandoned, there was a clip found on the underside with a disconnected wire. Investigators then looked into whether Todd Smith had been tracking Katrina with GPS. As the trial was nearing, Todd’s defense argued that the search of his computer should be thrown out of evidence because the search had been conducted by detectives, not an expert in forensic analysis of computers.

The State wrote a new search warrant and conducted the analysis again. Winnebago County State's attorney Marilyn Hite Ross told “20/20” that in the time between the first search in 2012 and the new analysis, technology had advanced.

“We actually were able to find evidence that Todd had used a tracking device. He actually had a file on Katrina. We believe that when Todd dumped the body, that he thought he had turned off the tracking device when he detached it from her vehicle. And he had not. It was actually still on. So, we had a GPS tracking of Todd from where we believe the body was dumped back to his home on the night of Oct. 22, 2012,” Ross said.

On Jan. 25, 2017, after five hours of deliberation, the jury found Todd Smith guilty of first-degree murder and all related charges. On April 4, 2017, Todd Smith was sentenced to 59 years in prison. During his sentencing hearing, Todd continued to proclaim his innocence.

In 2014, Todd had also been indicted for mail and wire fraud on those allegations that he was defrauding investigators. Before he could enter a plea, the government decided to dismiss those charges.

Paige attended the trial because she wanted to hear all of the evidence.

“After the verdict, I did not go to see him, but I talked to him on the phone, and I asked him to tell me what happened, and he wouldn't, because he immediately planned on appealing and trying to start that whole process. So, I was like, ‘OK. Even if you appeal, you're not going to win this. Just tell me the truth,’ and he still wouldn't.  And I said, ‘OK. You can either tell me the truth, or I won't be talking to you anymore, because I can't do this.’”

That was the last time she spoke to her father.

Todd Smith filed an appeal to overturn his murder conviction -- but it was denied.

ABC News' Xander Samaras and Naomi Shah contributed to this report.