Robert Guarante 1968 Booking Photo

Robert Gentile's connections with Robert Guarante, a bank robber seen above with a shirt over his head after an arrest in Natick, Mass., in 1968, intrigued federal authorities investigating the theft of half a billion dollars in art from Boston's Isabella Stewart Gardner Museum in March 1990. (William Rye / The Boston Globe)

It was a shore dinner in Maine a decade ago that transformed Robert Gentile, an aging, unremarkable wise guy from Hartford, into the best lead in years in one of the world's most baffling crime mysteries, the unsolved robbery of half a billion dollars in art from Boston's Isabella Stewart Gardner Museum.

Gentile disagrees with most of what the government says about him. But he does not dispute that he and his wife drove to Portland, Maine, from their home in Manchester. It was nothing then for the couple to jump into a car and cross New England for a meal. Gentile is said to be passionate about food. His nickname is "The Cook."

Neither is there disagreement that Gentile was meeting Robert Guarente and his wife. Guarente, a bank robber, moved from Boston to Maine in 2002, after his last prison sentence. He was living in the woods, two hours north of Portland. Guarente had been associated for years with three Boston criminals who the FBI believed were involved in or had information about the Gardner heist. One of the three was Guarente's nephew; another was Guarente's driver.

Gentile and Guarente had been friends and partners since the 1980s when they met at a used car auction. Federal prosecutors have said in court: They were inducted into the mafia together. They are believed to have "committed robberies and possibly other violent crimes together." And they roomed together for a while outside Boston while acting as "armed bodyguards" for the mafia capo who was their boss.

No one disputes that Gentile picked up the check in Portland. Or that he continues to complain that Guarente's wife, Elene, ordered an expensive lobster dinner.

What is disputed, hotly, is what happened outside in the parking lot. Elene Guarente has told the Gardner investigators that she believes her husband put one or more of the stolen paintings in their car before they left their home in the woods and that the art was handed off to Gentile in Portland.

Gentile claims that Elene Guarente's account, which she first gave investigators in 2009 or '10, is, as he once muttered in court, "lies, lies, all lies." Through his lawyers, he denies receiving a painting or paintings, denies having knowledge about the robbery and denies knowing what happened to the art afterward. Gentile said he met with Guarente in Portland because his friend, who died in January 2004, was sick, broke and in need of a loan.

Gentile's most emphatic denial may have come earlier this month when a federal judge sentenced him to 21/2 years in prison on what the government called unrelated drug and gun charges. At age 76, overweight, crippled by back injuries and suffering from a heart condition, Gentile pleaded guilty to the charges — knowing that doing so meant a certain prison sentence — in spite of an offer of leniency and a chance at the $5 million reward if he helped recover the art.

Gentile's lawyer, A. Ryan McGuigan, accused the FBI of concocting the drug case to pressure Gentile to cooperate in the Gardner investigation. The judge brushed aside the argument, concluding that Gentile did not need to be persuaded by an FBI informant to engage in the profitable sale of prescription painkillers. In any event, McGuigan said Gentile had nothing to trade the government for leniency or the reward, no matter how badly he wanted both.

As he settles into prison, Gentile could become another dead end in the succession of dead ends that have characterized the Gardner investigation. But the account of how he became, at least briefly, the best potential lead in the Gardner case offers a glimpse inside a sensational robbery from which the art world may never recover.

Gentile And The Gardner

The FBI will not discuss Gentile in the context of the Gardner robbery. But its interest has become apparent in other ways, including filings in court, a sensational press statement it issued in March, its pursuit of Gentile's Boston associates and a curious price list found in Gentile's home.

Buried among the guns and other odd items in Gentile's basement was a list of the stolen Gardner paintings and accompanying values. An infamous art thief from Massachusetts said recently that he wrote the list and that Gentile probably acquired it, in a transaction not directly related to the robbery that may have been nothing more than an attempted swindle.

There are signs, too, that government investigators are not persuaded by what one described as Gentile's consistent denials. A federal prosecutor said in court that an FBI polygraph examiner concluded there is a 99 percent probability that Gentile was not telling the truth last year when he denied knowing anything about the stolen art. Gentile's lawyer said the results are false because the test was improperly administered.

A year ago, dozens of FBI agents swarmed over Gentile's suburban yard. They found an empty hole someone had dug and apparently tried to conceal beneath a storage shed in his backyard.

Federal prosecutors said in court that Gentile was such a fixture in organized crime in Boston by the middle to late 1990s that he, with Guarente, was sworn in as a member of the Boston faction of a Mafia family that is active in Philadelphia. In a dramatic press statement in March 18, the FBI claimed the stolen paintings were moved to Connecticut, at least for a time, and to Pennsylvania. The bureau issued the statement on the 23rd anniversary of the robbery:

"The FBI believes with a high degree of confidence that in the years after the theft, the art was transported to Connecticut and the Philadelphia region, and some of the art was taken to Philadelphia, where it was offered for sale by those responsible for the theft. With that same confidence, we have identified the thieves, who are members of a criminal organization with a base in the mid-Atlantic states and New England."

Characteristically, the bureau will not elaborate.

Not only does Gentile deny being a member of the mafia, he denies knowingly associating with gangsters. If he is being truthful, people who know him say he is one of the world's most unlucky men because circumstance in which he has become entangled.

Some of the most important art ever created disappeared at about 1:30 a.m. on March 18, 1990, as St. Patrick's Day celebrations wound down across Boston. Two thieves dressed as police officers bluffed their way into the museum, a century-old, Italianate mansion full of uninsured art and protected by an outdated security system