What do we know about Sherlock’s Mary Morstan?

Ahead of Sherlock’s series 3 finale, we tot up what we know so far about this version of Mary Morstan. Speculation ahoy...

Warning: contains plot details for The Empty Hearse, The Sign Of Three and potentially spoiler-y speculation for His Last Vow (which we haven’t seen yet).

Something bad is going to happen in Sherlock. How could it not? The Sign Of Three was so cockle-warming an outing for Holmes and Watson, with such a cheering resolution (a baby! a disco! so many declarations of love!), that it had to be setting us up for a fall. A figurative one, this time.

Sherlock’s indestructibility established, the ‘something bad’ dangles Damoclean over other heads than his. There’s John of course, Mycroft, Molly, Lestrade, Mrs Hudson and the Woman, all of whom mean something to us and our hero. Another character though, one whose arrival could have signalled disruption and resentment but whose warmth, humour and winning portrayal by Amanda Abbington meant she ruffled not a feather, feels less safe.

We know so little about Mary Elizabeth Watson (née Morstan), a character imported from canon who clicked instantly and perfectly into Sherlock’s mechanics. If an axe is about to fall on the head of one of Holmes’ inner circle, first it’ll have to slice through the question mark hovering over Mary’s. If either, is she victim or trap?

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The window for speculation about her place in the series three finale will have closed come Horlicks time on Sunday, so let’s take this fleeting opportunity to tally up what we know at this point about Sherlock’s Mary Morstan…


She’s a clever, romantic, short-sighted, size 12, cat-loving, disillusioned Lib Dem-voting part-time nurse and only child who reads the Guardian, has a secret tattoo and an appendix scar, bakes her own bread and is both a linguist and a liar.

These all being deductions of Sherlock’s, we haven’t been yet privy to their proof (cleverness aside). How often, though, is the man wrong? How Holmes ascertained the existence of both tattoo and appendix scar on a fully dressed woman is a poser, but no more so than how he deduced her political disillusionment and lack of siblings. Anyone fancy a go at reverse-engineering those conclusions?

The most intriguing of these text-on-screen deductions has to be “liar”. We’ve seen Mary capable of light subterfuge with the imaginary ‘Beth’ code word and separately manipulating John and Sherlock to pair up on a case in The Sign Of Three. About what else though, and to whom, has Mary lied?


She first popped up on John H Watson’s blog

The tie-in blog that runs alongside Sherlock has gone to the trouble of creating fictional comments underneath John H Watson’s crime-solving posts. Mary’s first appearance in the universe of the BBC show came in these very comments. On the in-show date of the 20th of April, Mary replied to John’s comment that he just has to “keep going” during his grief with the reassuring words “And you will x”, quickly followed by “Let’s go for a drink later”. John’s as-yet unseen sister Harry, immediately replied, “Who’s Mary???”.

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Who indeed?

From “Let’s go for a drink” to a marriage proposal in under six months is fast work by most people’s standards (though, it should be said, the pair took it slowly in comparison with Watson’s proposal in the Conan Doyle story that introduced Mary, The Sign Of Four).

Other comments from ‘Mary’ on the BBC tie-in blog include words comforting John from trolls insisting Sherlock was a fake, expressing relief that John shaved off his moustache, and berating him for commenting that the Mayfly Man’s date-‘em-and-disappear MO was a “good trick”. She also appears in the blog posts themselves, tagging along once on a case and inspiring these words from the series’ John Watson:

“Oh, and in other news, I’ve got engaged. But, it’s not something I’m really going to talk about much here. I want to keep some things private. I will say, though, she’s the best thing that’s ever happened to me. Sorry, Sherlock :)”


She’s the best thing that’s ever have happened to John Watson

John thinks so, Mary agrees, Sherlock, with the line “Mary, when I say you deserve this man, it is the highest compliment of which I am capable” even allows that Mary Morstan is good for John, and the fans concur. Amanda Abbington’s Mary is warm, funny, clever and very welcome addition to Sherlock’s gang.

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If there’s any justice in the fictional world, come the close of His Last Vow, none of that will have changed. Whatever role Mary plays in the series three finale, pray that her essential goodness or love of John isn’t called into question. She may have secrets (more on that below), but we don’t want this version of Mary to go anywhere.

(Besides, if Mycroft knew at the drop of a hat which restaurant John had booked in The Empty Hearse, he’d surely have the low-down on any possibly threat mysterious Mary or her connections could pose to John or Sherlock.)


She’s an orphan

“You need to work on your half of the church, Mary. Looking a bit thin”, said Sherlock in The Sign Of Three. “An orphan’s lot” Mary replied, “Just friends. Lots of friends.”

In the course of solving The Sign Of Four, Conan Doyle’s Holmes revealed to Mary that her missing father was in fact dead, technically making her an orphan (for more on adult orphans, see The IT Crowd’s Roy in Italian For Beginners). When and in what circumstances did Sherlock’s Mary lose her parents? Did she ever know them? Who brought her up?


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She knows when Sherlock is fibbing

Nursing and bread-baking aren’t Mary’s only skills, she’s also shown a keen knack for distinguishing lies from truth, and an insight into human nature (about which Sherlock, as it’s been established, knows precisely nil).

As well as intuiting  that Sherlock’s plea to Major Sholto had worked and there was no need for John to break down his door in The Sign Of Three, Mary also told Holmes “I’m not John, I can tell when you’re fibbing”, a talent that could yet prove key to the events of His Last Vow.

(Incidentally, we hope it’s not a clue that when lovely Mary does the thumbs up in the above picture, she’s framed in the shot as if she has devilish horns…)


She’s pregnant

“I’ve never made a vow in my life and after tonight I never will again, so here in front of you all, my first and last vow. Mary and John, whatever it takes, whatever happens, from now on I swear I will always be there, always, for all three of you.” With those words Sherlock Holmes, human Clear Blue stick, announced that John and Mary were about to become parents, and to a real baby instead of a high-cheekboned high-functioning sociopath this time.

Sherlock leaps forward in time as suits the story, so how pregnant Mary will be in His Last Vow, or indeed, whether she’ll have had the baby by then, is all still to know.

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She’s a code-breaker

“Save souls now, John or James Watson…” began the text message that Mary quickly identified not as bible spam, but “a skip code” in The Empty Hearse, sending her off to Baker Street to make Sherlock Holmes drop his chips.

The speed of Mary’s code-breaking fits with Sherlock’s deductions of her cleverness and linguistic skills (she recalled Major Sholto’s room number before Sherlock did in The Sign Of Three, too), but perhaps the more interesting question is why the text message was sent to her, and not to Sherlock? After all, John was kidnapped from outside 221B Baker Street, not from his own house or surgery. The taunting messages continued to arrive on Mary’s phone, but were soon addressed to Sherlock, meaning that the person responsible for the kidnap was watching the rescue attempt.

That somebody, we assume, was the villain glimpsed reviewing video of John’s rescue at the end of the episode, the identity of whom Sherlock professed not to know. We know it was Charles Augustus Magnussen (Lars Mikkelsen), the BBC Sherlock’s version of C.A Milverton, heartless blackmailer extraordinaire from the Doyle stories. Something in the next entry suggests that Mary Morstan is no stranger to Magnussen…


She may have had previous dealings with Charles Augustus Magnussen

This one is indebted to the commenters who pointed out a detail from The Sign Of Three that passed me entirely by on first viewing: the wedding telegrams.

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A punch line in themselves for forcing Sherlock Holmes to suffer the indignity of reading aloud the words “big squishy cuddles”, the telegrams appeared to contain an allusion to the villain we’re expecting to meet in His Last Vow, the aforementioned Magnussen. If you’re up for a quick re-watch, start iPlayer at around 19:40 in the episode and watch Mary’s reaction as Sherlock reads out the telegram from “Cam”.

See it? Mary is visibly perturbed by the message, which seems innocuous enough (“Mary, lots of love poppet. Oodles of love and heaps of good wishes from Cam. Wish your family could have seen this”). Anyone noting her momentary distress on hearing the name, including John, can tell themselves it’s just an emotional day, but what if – as canny commenters have suggested – Cam is in fact, C.A.M, or Charles Augustus Magnussen?

What hold might the legendary blackmailer have over Mary? We await His Last Vow to find out.

His Last Vow airs on BBC One on Sunday the 12th of January at 8.30pm. Read our spoiler-filled review of The Sign Of Three, here.

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