One Florida country sheriff has a very hot cold case on his hands after a hit Netflix documentary unearthed new questions in a decades-old disappearance, and he opened up to Fox Nation's Nancy Grace about his investigation.

Among the cast of characters featured in the Netflix documentary "Tiger King: Murder, Mayhem and Madness" is Hillsborough County, Fla., animal sanctuary owner Carole Baskin.

She is also the former wife of Don Lewis, who went missing in 1997. Baskin vehemently denied any role in her husband's disappearance.

"A cold case is always open," said Hillsborough County Sheriff Chad Chronister on Fox Nation's "Crime Stories." "The last thing we did was back in 2011."

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"We asked [Baskin] to come in and take a polygraph and she declined," he continued. "And the year before, we took DNA samples from all Don Lewis' children -- in case that body was ever recovered, it would be in our database. We would be able to track it back that way."

The Netflix series is predominately focused on Baskin's arch-nemesis, Oklahoma zoo owner "Joe Exotic," real name Joseph Maldonado-Passage, who was convicted for plotting to murder Baskin.

But the documentary has created a surge of public interest in the Lewis case as well.

"[Lewis] is the first husband of Carole Baskin," explained New York Post reporter Michael Kaplan. "He had tried to get a restraining order on her. She claims he had Alzheimer's. They were not doing great as a couple, apparently.

"He was supposed to go on a trip to Central America," said Kaplan, "His car was found at the airport and he basically disappeared into thin air. He was never heard from again."

Chronister was a Hillsborough County Sheriff's deputy at the time that Lewis went missing, but he recalled that investigators could not determine that Lewis ever boarded a flight that day.

'TIGER KING' STARS: WHERE ARE THEY NOW?

"We checked all passenger manifests. Nothing showed up," said Chronister, adding that they did uncover one surprising fact. "For some reason -- and I don't completely understand -- why he had two passports. Neither one of them were flagged that he left the country as well."

Chronister also revealed that each passport used a different derivation of his name. "Donald is his middle name. So one was Jack. One was Don Lewis. He was going by two different names."

To hear more about Chronister's investigation, including what Grace thinks about the Tiger King's' murder-for-hire conviction go to Fox Nation and watch "Crime Stories with Nancy Grace."

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Fox News' Melissa Roberto contributed to this report.