Sherlock Episode 4.01 The Six Thatchers

Coming in 2017, Sherlock will return with three brand-new episodes that promise laughter, tears, shocks, surprises and extraordinary adventures. Season four begins with the mercurial Sherlock Holmes (Benedict Cumberbatch), back once more on British soil as Doctor Watson (Martin Freeman) and his wife Mary (Amanda Abbington) prepare for their biggest challenge yet: becoming parents.

In episode one of this new series, 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...