It was about 30 years ago when John Stamos developed an unlikely connection with the 1963 kidnapping of Frank Sinatra’s son.

"… I was at the Orange County Fair with [musicians] Jan and Dean, who I had a relationship with through the Beach Boys, and Dean [Torrence] turned to me and said, ‘Stamos, do you produce? Do you know how to get something made?’" the actor recalled to Yahoo! Entertainment on Wednesday.

"I was like, ‘Yeah!’" the 57-year-old shared. "And I didn’t. And he said, ‘Well, I got this story. My best friend kidnapped Frank Sinatra Jr. and I have the manuscript that he wrote in prison, and I have the rights to it. Let’s try to do something with it.'"

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John Stamos Wondery podcast

John Stamos has launched a 10-podcast titled "The Grand Scheme: Snatching Sinatra" airing on Wondery. It promises to offer the perspective of Barry Keenan, the man behind the kidnapping. (Photo by: Jordin Althaus/E! Entertainment/NBCU Photo Bank/NBCUniversal via Getty Images)

Recently, the "Fuller House" star has launched a 10-episode podcast titled "The Grand Scheme: Snatching Sinatra" airing on Wondery. It promises to offer the perspective of Barry Keenan, the man behind the kidnapping.

Sinatra Jr. was the middle child of Sinatra and his first wife, Nancy Barbato Sinatra, the mother of his three children. He followed his father into music as a teenager, eventually working for the senior Sinatra as his musical director and conductor.

But in 1963, three men kidnapped Sinatra Jr. at gunpoint from a venue the 19-year-old was performing in Lake Tahoe. According to the outlet, the kidnapping took place two weeks after the assassination of Sinatra’s onetime friend, President John F. Kennedy.

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Frank Sinatra kidnapping

Frank Sinatra speaks at a press conference for the first time since the capture of the kidnappers of Frank Sinatra Jr. in the driveway of his ex-wife's home. (Getty Images)

The kidnappers held Sinatra Jr. for a $240,000 ransom – the amount Keenan needed to pay his debuts – and turned down the $1 million Sinatra Sr. offered. Sinatra Jr. was released after 54 hours, and no one was physically hurt.

Within days, Keenan was arrested with the other two suspects, Johnny Irwin and Joe Amsler, and convicted of conspiracy and kidnapping. Investigators learned that Keenan was a high school friend of Sinatra Jr.’s sister, Nancy Sinatra.

Keenan masterminded the kidnapping, prosecutors said. He was sentenced to life plus 75 years in prison but was declared legally insane at the time of the crime. Keenan claimed that God told him to commit the crime via the car radio, the outlet noted. He had his sentence reduced and was paroled in 1968 after serving nearly five years.

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Frank Sinatra Jr. kidnapping

Frank Sinatra, Jr. meets with the press in front of his mother's home after being released by kidnappers. Frank Sinatra paid the kidnappers $240,000 in ransom for the release of his son. (Getty Images)

Sinatra Jr. went on to have a decades-long career as a performer. He passed away unexpectedly in 2016 at age 72 while on tour in Daytona Beach, Florida, the Sinatra family said in a statement to The Associated Press. He is survived by a son named Michael.

Sinatra Sr. died in 1998 at age 82.

According to the outlet, Stamos spent hours interviewing Keenan.

"The truth is, especially doing the podcast because now I have time to really explore his whole life, I mean, we’re talking about a mentally ill man, you know, who was addicted to pills and booze and had a very dark, troubled childhood of religion and mental illness that got swept under the carpet because that’s what they did in the ‘40s and ‘50s," Stamos explained.

"You know, he started hearing voices and he told his aunt, who was Catholic – she wasn’t a nun but she was really involved in the Catholic Church – and she said, ‘Don’t tell anybody,’" Stamos continued. "Assimilate. Assimilate. And he spent his whole life not being who he was. And he ran into a lot of hard knocks, and he’s always looking for a shortcut. He wanted a seat at the table, and he was gonna do everything he could to get it."

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Barry Keenan Frank Sinatra Jr.

This photo shows Barry Worthington Keenan, 23, whom the FBI arrested on December 14th in connection with the kidnapping of Frank Sinatra Jr., 19. John W. Irwin and Clyde Amsler, 23 were two other accomplices. Keenan and Amsler were arrested in the Los Angeles area. Irwin was arrested in San Diego. Authorities said most of the $240,000 ransom which was paid has been recovered. The Sinatra youth, a singer, was taken from his motel room at the state line of Nevada, by two gunmen on December 8th. He was released unharmed in the Los Angeles area early December 11th, after the ransom had been paid. (Getty Images)

Stamos told the outlet that Keenan doesn’t take the idea of the kidnapping lightly. Stamos said he hopes the podcast will dispel any conspiracy theories that continue to exist about the kidnapping, including the claim that Sinatra Jr. was in on it.

"He’s done a lot of healing," said the star about Keenan. "He’s done a lot of work in prison reform with prisoners. He’s done a lot of work in the substance abuse area. He’s an [Alcoholics Anonymous] guy, has helped a lot of people, so I think he’s tried to redeem himself. He’s always, through the podcast, he’s talking about the state of grace. He’s always trying to reach the state of grace, and I said at the end, ‘Have you reached your state of grace, Barry?’ He said, ‘Yeah, but I’m still, I’m a work in progress.’"

The Associated Press contributed to this report.