What was arguably the art theft of the century happened on 18 March 1990, when two men dressed as police officers forced their way into the Isabella Stewart Gardner Museum in Boston and made off with the paintings valued at $300m.
Among the works were two Rembrandts, A Lady and a Gentleman in Black and Storm on the Sea of Galilee, the only known seascape by the painter, as well as Vermeer's The Concert. Also purloined that morning were paintings by Manet.
Years of investigation by the FBI, which made the capture of the art thieves a highest priority, yielded a zero.
Until, that is, a shady antiques dealer in Boston, facing charges of drugs and weapons possession, came forward recently, claiming that he knew the whereabouts of the missing art.
William Youngworth told the FBI that he and an art-thief friend serving time in a federal prison, Myles Connor, had information that would lead agents to recovering the long-lost works. Both men were serving prison terms at the time of the theft and could not have been directly involved.
In return for the information, Mr Youngworth demanded immunity from all charges filed against him, the release of Connor from prison and the $5m (pounds 2.9m) reward still outstanding for the return of the paintings. Mr Youngworth repeated his demands in a television interview broadcast on Wednesday evening.
Understandably, the Gardner museum is excited. Formal contacts between its lawyers and representatives of Mr Youngworth are under way.
Yesterday Connor was temporarily transferred from his cell in Pennsylvania to Boston to enter serious negotiations with the FBI.
Neither man has a reputation that invites trust from the authorities. Mr Youngworth, 38, has a history of forgery and making false claims. Connor, 54, allegedly Mr Youngworth's mentor, was a night-club rock singer in the Sixties and Seventies, authorities said, before beginning a career of crime.
The men do, however, have some special credibility in this instance.
Connor, in particular, has a history of stealing art works and then securing leniency from prosecutors by turning up other treasures already missing.
In 1975, for instance, he pleaded guilty to stealing Andrew Wyeth paintings from a Maine estate but escaped jail by directing prosecutors to a $5m Rembrandt stolen previously from the Boston Museum of Fine Arts.
Serious attention started being paid to Mr Youngworth last week after it was disclosed that he had secretly arranged a visit by a reporter from the Boston Herald newspaper to see one of the paintings.
The reporter, Tom Mashberg, was apparently taken to a warehouse somewhere in New England and, by dim torchlight, shown Rembrandt's Storm on the Sea of Galilee.
Under the front-page headline "WE'VE SEEN IT!", the Herald printed the astonishing tale last week.
Mr Mashberg is not an art expert, nor was he allowed to touch the painting he was being shown. But after a long meeting between him and the directors of the Gardner museum, the latter said it was taking Mr Youngworth's claim seriously.
What Mr Mashberg had seen, the museum said, was either "an extremely good copy or it was the Gardner painting".
It is not clear whether Mr Youngworth or Connor are acquainted with the Gardner thieves or if they even know their identity.
Mr Youngworth, who faces a hearing on his drugs and weapons charges in Boston today, is expected to meet federal agents to discuss the paintings immediately afterwards.
In spite of the murkiness of the affair, some experts are daring to hope that the missing treasures may be hanging in the Gardner once more within weeks.
"This is the most interesting lead yet," suggested Constance Lowenthal, of the International Foundation for Art Research in New York, which specialises in tracking down stolen works. "They're either hoaxers or go-betweens. We don't know yet, do we?"
The Gardner, meanwhile, is unapologetic about giving credence to Mr Youngworth and his claims.
Joan Norris, the museum's marketing director, said that the significance of the 1990 theft is "so great that the Gardner must do everything we can to recover those works of art".