Sherlock Season 4 is shaping up to be a big one, between a theatrical release and the latest trailer, but will our 2017 premiere dive right into the Moriarty cliffhanger that ended Season 3? Perhaps not, as our full synopsis for “The Six Thatchers” teases an update on a classic tale, along with a deeper exploration of Mary’s past.

The BBC released a first official synopsis for January 1 return “The Six Thatchers,” itself an update of Sir Arthur Conan Doyle’s “The Adventure of the Six Napoleons.” As we saw with “The Abominable Bride,” Season 4 isn’t quite going to return the focus to Moriarty out of the gate, but we’ll at least keep on peeling layers of Mary’s past:

In episode one of this new series, written by Mark Gatiss, Sherlock waits to see where Moriarty will make his posthumous move.

One mysterious case in particular baffles Scotland Yard - but Sherlock is more interested in a seemingly-trivial detail. Why is someone destroying images of the late Prime Minister Margaret Thatcher? Is there a madman on the loose? Or is there a much darker purpose at work? Something with its roots deep in Mary Watson’s past…

Benedict Cumberbatch returns as Sherlock Holmes, with Martin Freeman as John Watson, Mark Gatiss as Mycroft, Rupert Graves as Inspector Lestrade, Una Stubbs as Mrs Hudson, Amanda Abbington as Mary Watson and Louise Brealey as Molly Hooper.

The new season is also likely our last Sherlock for the foreseeable future, while “Six Thatchers” was directed by Doctor Who and The Flash director Rachel Talalay

In the meantime, watch the newest Sherlock Season 4 trailer below, and stay tuned for more.