The New Year's Day episode of 'Sherlock' was one of the most surprising and divisive yet. A shocking death, a fractured friendship and the ghost of Moriarty plagues this episode, and indeed will no doubt continue to do so in the next two airings.

SherlockSherlock returns with Moriarty on his mind

Death seems to line the plot throughout the episode, with frequent references to the Grim Reaper fable 'Appointment at Samarra'. Plus, in his obsession that every sinister thing that happens is something to do with Moriarty, Sherlock makes a few fatal oversights.

Sherlock (Benedict Cumberbatch) has been somewhat absolved of the killing of Charles Augustus Magnussen from 'His Last Vow' thanks to his government official brother Mycroft (Mark Gatiss), but that hardly means the detective can just sit back and relax. He has another case to solve: several busts of Margaret Thatcher have been destroyed after a series of break-ins in different houses and it doesn't take him long to discover that someone is looking for something. They find it too; he catches the gun-wielding culprit upon discovering a memory stick hidden the bust that is exactly the same as the one Mary (Amanda Abbington) gave to John Watson (Martin Freeman) to explain her past - one that was supposedly destroyed.

The plot turns on to Mary once again as one of her former teammates Ajay is seeking revenge after her 'betrayal'. Sherlock repeatedly promises to protect Mary from harm, but that doesn't stop her gallivanting off to protect John and their baby daughter Rosamund. It's an underestimation of the Baker Street sleuth on Mary's part because he soon tracks her down again, discovers that she hasn't betrayed anyone and that the real villain of the piece was a supposedly serene old secretary. And then both of them underestimate said secretary, and Mary finds herself taking a bullet for Sherlock and subsequently dying.

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Poor John Watson. After discovering that there have been more lies on Mary's part about her past, he is now a widower who has a daughter to raise single-handedly - especially since now he doesn't want to speak to Sherlock despite the latter's best efforts. But don't feel too sorry for him. It emerges that Watson has been sending flirty messages to some woman he met in the street for quite some time now - and we bet that's something that even Sherlock couldn't have foreseen. The real question is of course, who is this woman?

The next episode of 'Sherlock' - 'The Lying Detective' - will air on Sunday (January 8th 2017).