As reported by Deadline.com, Abbington’s mystery role will “significantly impact” the lives of Sherlock (Benedict Cumberbatch) and Watson. When combined with the hint that, according to producer Steven Moffat, one of Season 3’s key words was “wedding,” the signs point to some sort of love interest.
There’s also the fact that Abbington and Freeman have been real-life partners for years. So you know there would be chemistry between Watson and the mystery lady.
Alas, it will probably be a long time before we know the exact purpose of Abbington’s character on “Sherlock.” New episodes of the British series are not expected until the winter of 2014. There is no definitive word yet on whether Abbington will appear in just one episode (presumably the first, “The Empty Hearse” in which Sherlock reveals that he faked his own death) or if she will recur throughout the season.