What kind of a best man is Sherlock Holmes? That question will be answered in the second episode of “Sherlock” Season 3, “The Sign of Three.” A video clip from the episode indicates that the results of this social experiment could be amusing.

If nothing else, there’s a brain.

The central event in “The Sign of Three” is John Watson’s (Martin Freeman) wedding to Mary Morstan (Amanda Abbington). As other characters realize right at the beginning of the clip, Watson is certain to ask Holmes (Benedict Cumberbatch) to be his best man.

But that means a speech. There are also a whole lot of other wedding traditions that Sherlock will have to face in this oddest of mysteries. Also, because this is “Sherlock,” we can expect the detective to solve a murder or two before the reception is over.

“The Sign of Three” airs Sunday, Jan. 26 on PBS.

Posted by:Laurel Brown