BOSTON (CBS) – The hunt for the thieves behind the 1990 Gardner Museum heist has taken an unexpected turn.

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Investigators are now focusing on the nightwatchman on duty the night of the theft, according to a report from the Boston Globe.

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Richard Abath was thought to be a victim when police found him handcuffed and duct-taped after the robbery.

But now, federal prosecutors want to know why his footsteps are the only ones leading up to a stolen painting.

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Abath maintains his innocence.