After over a year since the throwback stylings of 'The Abominable Bride', ''Sherlock'' is back on TV screens for three more feature length episodes. Armed with the hook of Moriarty's evil potentially reaching from beyond the grave, Steven Moffat and Mark Gatiss have a lot of hype to live up to in what may be the last new adventures for Britain's greatest sleuths.

'The Six Thatchers' by Gatiss sees Sherlock investigating the strange destruction of marble busts of former, as well as late and controversial, British Prime Minister Margaret Thatcher, believing them to be connected to Moriarty.

As he digs deeper, however, Sherlock and new parents John and Mary find themselves tied up in a web of revenge, intrigue and ghosts.

Returning to the basics

The plot, itself loosely based on Conan Doyle's 'The Adventure of the Six Napoleons', does a decent job at getting the audience back into this world and hooking with a compelling, albeit ultimately implausible, notion. Gatiss gives us a story that goes through the expected formula: a winding conspiracy, unrelated and mundane events connecting, an examination of the changing dynamic between an aging Holmes and Watson as the latter moves into fatherhood. The relationship element is probably the real strength of the episode, as the dynamic between Holmes, Watson and Mary veers from fun and bubbly to deathly serious and even painful.

You get many angles on their relationships and it adds more dimension.

Cumberbatch and Freeman are solid as ever, reminding us why they brought Conan Doyle's creations back into the mainstream, but it's really Amanda Abbington as Mary who gets the emotional meat of the story and is superb. A confident woman and former killer whose ties force her into a bad situation, but her loyalty and love of John pushes her onwards to protect him and their baby.

Abbington really hits it out of the park with a wonderfully varied but heartfelt TV performance that almost upstages her co-stars.

Not much new

It's hard for me to have a definitive feeling yet, as we've two more episodes to go, as to how good the episode ultimately was. On its own, Gatiss gives us the requisite checklist, well paced and never lacking in focus or direction, but there's little new or different here from past ''Sherlock'' stories that followed a similar formula (even the use of Thatcher feels less inventive than it should be), and no real surprises.

Still, fellow Doctor Who veteran Rachael Talalay gives us a sleek and stylish episode, with some wonderfully creative editing, such as a recreation of the episode's first big crime, and a bare-knuckle fight with some great sound design.

In the end, 'The Six Thatchers' is a good hour and a half of crime TV, well produced and acted, but next week's needs to step up the game in order to really push ''Sherlock'' into more exciting mystery territory. The last act, when the emotions go into high, almost elevate the episode over being merely being good enough, but familiarity prevents it from doing so.