At last the mystery of the $500 million Isabella Stewart Gardner Museum heist may finally be solved, because “Sherlock” is on the case!

Benedict Cumberbatch, star of the PBS series on famous fictional detective Sherlock Holmes, did a tour of the museum earlier this week with head of security Anthony Amore. We’re told they retraced the steps of the infamous 1990 heist, when thieves, dressed as Boston police, handcuffed museum guards and made off with 13 priceless works of art. No doubt Sherlock stopped at the empty frames where some of the missing masterpieces once hung.

The stolen works include three Rembrandts — most notably, “The Storm on the Sea of Galilee”; Vermeer’s “The Concert”; Govaert Flinck’s “Landscape With an Obelisk”; five works on paper by the impressionist artist Edgar Degas; Edouard Manet’s “Chez Tortoni”; a Chinese vase; and a finial from a pole support for a Napoleonic flag.

“He came in for a little tour,” museum spokesgal Jennifer Rosenberg told the Track. “He met some of the staff. He loved the museum and spent quite a bit of time walking around looking at different things. I guess he was an art history major, so he appreciated the historic value of the collections.”

Cumberbatch, who was nominated for an Emmy yesterday for outstanding lead actor in a miniseries or a movie for his portrayal of an updated character based on the iconic British detective, is in town to play former Senate prez Billy Bulger in the Johnny Depp flick “Black Mass,” about Billy’s?big bro, Southie gangster Whitey Bulger.

The BBC recently announced that “Sherlock” would return for a fourth season in 2015.

File Under: The Art of Deduction.