(CNN) -- Like a magician in a blue shirt and white socks, James Riddle Hoffa stood outside the Machus Red Fox restaurant in Michigan on July 30, 1975, made a phone call, and vanished.
Some people would later say he seemed nervous as he headed to a supposed meeting there with suspected mob bosses. Some would say they saw a mysterious car leaving the lot. But the one question no one has yet answered for investigators is the essential one: Where did he go?
Now, once again, as they have so many times before, FBI agents and other officers are digging. Once again, the lead has come from someone with ties to organized crime. And once again, the target is a nondescript field where Hoffa might...just might...be buried.
All that changes is the details.
This time the story being told involves Hoffa being beaten with a shovel, and buried alive beneath the concrete slab of a now long-gone barn.
Oakland County Sheriff Mike Burchard says, "It is my fondest hope that we can give that closure not only to the Hoffa family but also to the community to stop tearing that scab off with every new lead and bring some conclusion."
Hoffa's life came to its mysterious conclusion after decades of truly remarkable accomplishments. Born in Indiana, he became interested in organized labor as a teenager when he encountered unfair working conditions. As he grew into adulthood, he became more assertive about organizing unions, and gradually he became the leader of the Teamsters, transforming that union into a political juggernaut capable of making or breaking candidates.
It was his passion. On a grainy old piece of film from the Canadian Broadcasting Corporation in 1960 you can still see him in his office near the Capitol in Washington. He bristles when the reporter asks if he has any hobbies, like golfing. "Seven days a week," Hoffa says, "I have more fun here working than anybody can have on a golf course or any sport you can name."
Hoffa's bare-knuckled, win-at-all-costs approach to the union business, however, took him down some dark roads.
He struck deals with organized crime leaders. He broke laws. And eventually he was sent to prison.
In what looked like a sketchy -- if unproven -- deal for political support, President Richard Nixon pardoned him, and the Teamsters lined up behind Nixon's successful reelection campaign.
But even Nixon's help came with a price: Hoffa was told he had to stay out of the union business. Still, Hoffa fought to regain his power anyway, and soon a lot of people in a lot of places arguably had reasons to want him gone. Then he was. And ever since, people have looked for him.
More than a dozen times investigators have followed what are invariably described as "credible" leads to a suspected Hoffa burial site. Michigan has produced the most locations, and Hoffafiles often refer to them by their distinguishing features, making conversation sound like a list of a Richard Stark novels: The Horse Farm Grave. The Dead Man's Dumpster.
New Jersey, with its long history of Wise Guys (cue the "Sopranos" theme) has also excited attention in the hunt for Hoffa. One of the most popular theories is that he was encased in the cement of Giants Stadium.
And on and on the theories go. He was sunk in the swamps of Florida. He was carted off to California. He was crushed in a car and shipped overseas with a load of scrap metal. Sometimes the possibilities seem as endless as the searches.
All of this is not cheap.
Based on the sticker price of just one search as analyzed by the Detroit News, it is not unreasonable to estimate that police agencies have spent well over $3 million trying to find this man. Or more to the point: his body. He was legally declared dead in 1982, and even if he had been miraculously living incognito in Toledo all these years, he would be 100 years old.
Strangely, there seems little debate about what most likely happened.
True crime aficionados and authorities alike have long believed that Hoffa's dreams of a comeback did not sit so well with mobsters who'd settled into a new routine while Hoffa was away. And, they theorize, because he would not go into a quiet retirement, the "muscle" showed up and retired him another way. The details are the problem. Precisely who did it? Precisely how? Police know you can't make much of a criminal case based on, "We're pretty sure he's dead, and we're pretty sure it was these guys."
Hoffa's family has responded to the latest tip and search as they always do, by suggesting they hope it works. But 38 years after the man who was the ruling face of big labor disappeared in the clear light of day, no one has yet been able to throw aside the curtain, untangle the riddle, and declare "We have found him."
For now, James Riddle Hoffa, is still hiding.