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EXCLUSIVE: Robert Stack never lost hope that some of the country’s most shocking cold cases could be solved.

The veteran actor, who earned an Emmy as the tough-guy hero of TV’s "Untouchables" and an Oscar nomination at the height of his movie fame in the ‘50s, died in 2003 at age 84. 

He is still celebrated today as the iconic host of "Unsolved Mysteries," a docuseries that detailed crimes, tales of lost love, cases surrounding missing persons, paranormal encounters and other unexplainable events from over the years.

The Emmy-nominated show originally premiered in 1988 on NBC. For decades, it lived on various networks and cable channels. "Unsolved Mysteries" returned in 2020 on Netflix.

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Robert Stack hosted 'Unsolved Mysteries' from 1987 until 2002.

Robert Stack hosted 'Unsolved Mysteries' from 1987 until 2002. (Margaret Norton/NBCU Photo Bank/NBCUniversal via Getty Images via Getty Images)

"Bob was such a fan of the show," co-creator Terry Dunn Meurer, who has been with the franchise since its first iteration, told Fox News. "He would get so involved in the stories. He wasn’t just a host who read copy. He became really involved. He would ask questions about the episodes. He really, really cared in a sincere way about these cases."

"He embraced the entire premise of ‘Unsolved Mysteries,’" Dunn Meurer continued. "He would also get really excited when a case was solved or a new update came in. There are so many stories I could tell you about Bob, but that’s how I remember him best. He cared so much about these stories and the people who were involved. He never shied away from asking questions after he saw a script and he always hoped something would come from them."

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"Unsolved Mysteries," one of the longest-running programs in television history, was the first series to offer an audience-driven "call to action," urging viewers to share tips that could help solve real cases. 

Now, fans can continue to do just that with the "Unsolved Mysteries" podcast. Just like the television show and Netflix streaming series, each episode concludes with a "call to action" - encouraging listeners to visit unsolved.com and provide clues that could help solve their featured mysteries. 

Robert Stack was a celebrated actor before he took on the role of host for 'Unsolved Mysteries'.

Robert Stack was a celebrated actor before he took on the role of host for 'Unsolved Mysteries'. (Walt Disney Television via Getty Images)

Each week, the podcast will unveil a new case and feature interviews with family members associated with the stories, as well as forensics experts and law enforcement.

"I know a lot of people consider us to be ‘true-crime,’ but we think of ourselves more as a mystery brand," Dunn Meurer explained. "We try to offer something for everyone. There’s murder, disappearances, UFOs and ghosts. We offer a combination of stories to bring people together. For me personally, the reincarnation stories that we produced in the old episodes have always intrigued me. They’re so hard to explain. How could someone have memories from a previous life? Were they channeling a spirit from somewhere or was it something more? I know it has always interested me."

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Dunn Meurer is hopeful the podcast can help decode some new mysteries with the help of listeners. She said the TV show helped solved about 260 cases alone. And while not all the mysteries are solvable, such as those involving ghosts and UFOs, she insisted tips come in daily.

"We work with law enforcement if it’s a criminal case," she said. "So at the end of each episode, we let listeners know how they can help. We then take any tips that come in and give them to law enforcement."

The 'Unsolved Mysteries' podcast is hosted by Steve French.

The 'Unsolved Mysteries' podcast is hosted by Steve French. (Cadence13)

"And we’re always thrilled when a tip comes in," she continued. "We still have tips coming in even from the launch of the Netflix series. And I read them all. We get very excited because sometimes we do get very good tips that law enforcement can follow up on. And with the podcast, listeners can always go back to an episode and revisit a story. Law enforcement also keeps in touch with us. I guess that’s the satisfying part of doing the show and the podcast - the fact that we’re getting so many great leads. It feels like we’re achieving the mission of the show - to try and help solve some mysteries."

And it’s not just tips that come in daily. Dunn Meurer said new cases are submitted every day, so chances are "Unsolved Mysteries" will never run out of stories to tell.

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"We have a team of researchers that go through every case," she said. "Sometimes law enforcement doesn’t want us to do a case because perhaps they’re nervous some of their evidence will get leaked out to the public. And we do look for cases that have twists and turns. Sometimes a person disappears one day and there are no leads or suspects. There are theories of what happened, but nobody can figure out a motive. Those cases are harder to do because they don’t have anything for our listeners to latch onto so they can help. Those cases are certainly more challenging. But we review everything that comes in."

Dunn Meurer said that over the years, "Unsolved Mysteries" has received support from law enforcement. She said the show helps raise awareness on local cases, presenting them on a national level, which is essential in receiving tips.

"We get cases all the time submitted on our website," she said. "People reach out to us all the time, asking us to tell their stories. Because they know the power of the media. And that’s one way people can make sure law enforcement keeps these cases alive. Because a lot of the cases we cover aren’t the high-profiled ones you read about in the headlines. They’re the smaller stories from smaller towns. And at a certain point, no more leads come in. That’s when they come to us. And the mission of the show is to help solve mysteries. So the more mysteries we can put out there, then hopefully, the more leads could come in. And maybe, something will get solved. That’s the hope."

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In reflecting on the lasting success of "Unsolved Mysteries," Dunn Meurer said that genuine curiosity - like the one Stack possessed - is what has kept fans together for decades.

"When we first started the show, we weren’t sure if the audience would want to listen to stories about unsolved cases," she said. "But what we’ve learned over the years is that people are truly intrigued. And they’re hopeful. Even though some of these stories are tragic and dark, there’s always the hope that one day we will have the answers."

A new episode of the "Unsolved Mysteries" podcast is released every Wednesday. The Associated Press contributed to this report.