Watch the two-hour special, "Riddle: The Search for James R. Hoffa," on Fox Nation. Fox Nation is a streaming subscription service you can access from your phone, computer and select TV devices. We've created a members-only destination for Fox News' most passionate and loyal fans featuring exclusive content, exclusive experiences and exclusive access.

In this episode you'll hear from Melvin Gudknecht, a former special agent in the intelligence division of the IRS. Gudknecht was part of the prosecution team that put Frank Sheeran in federal prison, and believe it or not says Sheeran, despite being an admitted mafia hitman, was one of the most honorable people he ever met.

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