Rick Abath might have been less inclined to follow the orders of the two men disguised as police officers who robbed the Isabella Stewart Gardner Museum of its masterpieces if he did not have a ticket to that night’s performance of the Grateful Dead.

Shortly after he buzzed the two thieves into the museum — falling for their ruse that they were Boston police officers investigating a "disturbance" — Abath made a second grievous error. Told that he looked like someone that police were looking for on an unrelated crime, he followed the instructions that one of them gave to step out from behind the museum’s security desk so they could get a “good look” at him.

In doing so, Abath removed himself from the museum's only panic button, the only way that he might summon real police to an emergency inside the building. As Abath told me years later, he feared that if he didn't follow instructions, he would put himself at risk of being arrested — and miss seeing his favorite rock group perform in Hartford that Sunday night.

While attentive to the responsibilities of his job, Abath acknowledged that he could be casual about adhering to its details. He had been attracted to the work as night watchman the year before because it gave him the time and freedom to carry on his real purpose in life at the time — to play in a rock band. As long as he showed up for the start of his midnight shift, it didn't matter if he was drunk or stoned, which he confessed he at times was, because nothing ever happened and he'd sober up in time to complete his rounds and the other sundry duties of being a night watchman.

Abath told me, when I interviewed him in early 2005, that he had let several of his friends into the museum a couple months before the theft to celebrate New Year's Eve, partying with drugs and booze amid the museum's priceless collection. He told me he had figured out how to avoid having his appearance picked up by the sensors that were embedded in each gallery's doorways as part of the museum's motion detector system during his rounds. (It should be noted that an independent museum security analyst tried doing so after the heist and determined it would be impossible to do this.)

Over the years I interviewed him, Abath expressed little regret that his actions may have contributed to the heist. He once explained that he was just glad to be alive, having feared for his life the night of the robbery.

In an interview with me, Abath consistently blamed his actions the night of the heist on his inadequate training. As others later confirmed, Abath said he was always complaining to his security supervisors about shortcomings in the guards and night watchmen's training and in the equipment they had available to them.

Night watchman Rick Abath as he was found the morning after two thieves bound him in duct tape and tied him up in the basement of the Gardner Museum. (Courtesy "Master Thieves")

After he and his fellow night watchman were found by authorities shackled in the museum's basement, Abath made it to Hartford for the Grateful Dead. His conscience, he told me, was clear. He had been planning on staying over to see the band play on Monday night as well, until he saw the headlines in the morning newspapers reporting that more than $200 million worth of artwork had been stolen. He realized that leaving town and staying away would not look good for the guy who had let the thieves into the museum.

Abath needn’t have had to worry. He contended that he passed a lie detector test, and after, FBI agents didn't pressed him about his actions the night of the theft or any possible complicity with those who pulled it off for decades. (But in a more recent interview with me, he recounted how the feds had approached him in Brattleboro in 2010 — the first time in 20 years — and told him, among other things, that they'd never stopped considering him a suspect.)

He has since gone before a federal grand jury and, until he stopped talking to reporters a couple of years ago, appeared in occasional news shows always denying any complicity in the theft. But the delay in pressing him about his actions right after the heist has given him a defense that he didn’t have in 1990 — forgotten memory.

Three years ago, the assistant U.S. attorney overseeing the investigation pressed the FBI to look at the videotapes of activities at the museum in the nights before the theft to check out one of Abath’s assertions. The tape from the night before the theft revealed an incredible surprise — Abath had let someone into the museum. After a brief conversation with him at the security desk, the man left. The tape was released to the media and gave rise to the speculation that the visitor might have had something to do with the theft.

Although authorities would later acknowledge that the encounter was an innocent one and the night-before visitor had no connection to the theft, Abath was useless to them when asked about the encounter. It had taken place 25 years before, he told them, and he had no idea of who the man might have been. (Through our reporting for Last Seen, we confirmed a Globe account in November 2015 that determined that the night before visitor was the deputy director of security for the museum.)

Although he told me he realizes that he will go down in history as being the person who opened the door that led to the largest art theft in history, Abath said he was intent on making sure the incident did not define his life. When we last spoke in 2014, he told me he was proud that he helped in raising two children, was married and was working as a teacher’s aide at a public school in southern Vermont. He said he even was writing a memoir as a thesis for a graduate degree and would include a full account of what he remembers about what happened that fateful night.

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