When Geraldo Rivera cracked open Al Ca-pone’s secret vault on live TV on April 27, 1986, America didn’t know what to expect. Big Al’s best silk boxers? His favorite baseball bat? An Eliot Ness dartboard? Anticipation was high, and Rivera, already renowned for theatrics as an ABC news reporter, played to the audience with trademark skill. Standing in the basement of Chicago’s abandoned Lexington Hotel, once the notorious prohibition-era gangster’s headquarters and site of the vault, Rivera breathlessly proclaimed, ”This mystery is going to be resolved!” Then he blasted away with a Thompson submachine gun and blew down a chunk of wall using a gangster-style dynamite plunger.

But the payoff, alas, never came. After nearly two hours of frenzied buildup, with IRS agents and police crime-lab technicians standing by in case loot-or bodies-were unearthed, Rivera gathered his excavation crew around him, peered into the hole, and admitted to the folks at home that what he had turned up was pure dirt.

At the end of the show, a clearly dejected Rivera apologized to the audience. ”What can I say?” he asked. ”I’m sorry. See ya next time.” And with that, he departed down a long, dark tunnel singing ”Chicago.”

But that wasn’t the end of the search. ”We really didn’t give up for a couple of days afterward,” recalls Doug Llewelyn, one of the show’s producers. ”We dug so far out under Michigan Avenue that the sidewalk caved in and we had to replace it.” Still, they found nothing.

In his 1991 autobiography, Exposing Myself, Rivera said that at first he felt the show was a disaster. Then he saw the overnight ratings: 30 million homes, making The Mystery of Al Capone’s Vault the most-watched syndicated TV special ever, a rank it still holds. Wrote Rivera: ”My career was not over, I knew, but had just begun. And all because of a silly, high-concept stunt that failed to deliver on its titillating promise.”