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

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

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.

Abath maintains his innocence.