In the Sherlock episode His Last Vow we see in detail how Sherlock has plotted to gain access to the villain Magnussen's apartment despite tight security.

But when He gets there he finds that Mary is already there.

How did she gain access to the apartment?

3 Answers 3


This is deliberately left ambiguous, possibly so further details of Mary's past can be explored in further episodes.

There is no stated explanation for this: the elaborate plan (months in the making) Sherlock has devised to gain access to Magnussen's apartment is not recounted to in order to highlight the level of security involved, but as a 'bait-and-switch' plot device to deliver an unexpected payoff when we find an Assassin in the apartment, and the identity of this Assassin to be Mary. 'Claire De La Lune' is exactly the same device being executed in another manner.

It's just a very attentive, preemptive writing technique that anticipates viewer response to clues (and importantly doesn't condescend to them) and then reveals it to be misdirection. This is the legacy of meta-cinematography, finally finding itself in television.

Sherlock has already made it very clear that it doesn't necessarily believe in hand-holding the audience through individual plot details, as demonstrated by the still not fully resolved Reichenbach Fall.

It leaves people to speculate, but never resolves fully: It's part of its charm. It will likely never be disclosed, but it won't stop people from enjoying speculating on here!

They're goading us with something we don't have the pieces to resolve, and paying lip service to our need as an audience to know every detail by removing the opportunity to do so.

This is quite funnily appropriate for this site: They're turning us all into Andersons

  • The thing is, we might have the pieces to resolve. That's what keeps us going. Co-showrunner Moffat is now well-known for laying down groundwork that seems like throw-away bits or unimportant "filler." That OH IT WAS THERE ALL ALONG reveal. Jan 13, 2014 at 4:25
  • 1
    If it was just a storytelling technique to give the "Mary reveal" more gravitas, then I see no reason why it wasn't explained later, when Sherlock, John and Mary sit down to talk. Instead, Sherlock just says "... then you left the way you came." - Due to my frustration about the flaws/inconsistencies of the "Lazarus" explanation I wouldn't be surprised if the writers don't actually have a sound explanation for this either.
    – Oliver_C
    Jan 13, 2014 at 14:00

From an interview with Mark Gatiss and Steven Moffat:


  • We had her doing all sorts of acrobatics, didn’t we? He actually, at one point, goes over and finds the window open and all that.

    But it was just boring, so we didn’t have it. She got in ingeniously.


  • She broke in.


  • She’s a highly trained intelligence agent, who’s doing a lot better job of breaking in than John and Sherlock are.

    And if you actually think this through, suppose Sherlock hadn’t blundered his way in that night? She’d just have shot Magnussen, gone back to being Mrs. Watson – and not only that, they’d have carried on solving crimes together, with this lethal killer nurse wandering along behind them, picking off anyone who might put them in danger. That would’ve been the show.

  • If she just broke in, what was the point of befriending Janine? Just to get his schedule? - But wasn't he supposed to be out for dinner that evening? Isn't that why Sherlock chose that time to break in (he wanted to steal the letters).
    – Oliver_C
    Jan 17, 2014 at 22:30
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    it's undisclosed, that's all. As an audience, we don't need to know why she befriended Janine, and for what purpose. It's bold, and non-condescending to leave it open. If every detail were disclosed, it would make for pretty dire television. Quit being an Andersons and let it go! ;) Jan 17, 2014 at 23:52
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    Not spoon-feeding the audience everything is actually something I appreciate. As long as we are given all the necessary clues to figure it out ourselves. - It's like with the "Fall" explanation. It's not about being dissapointed, because that's subjective, it's about being logically sound. This is a Sherlock Holmes story after all.
    – Oliver_C
    Jan 18, 2014 at 10:33

Apart from John's answer there is another explanation, Janine is the P.A of Charles Augustus Magnussen. She is also a good friend of Mary, because she was the bridesmaid. So maybe Janine let her in.

  • 1
    Looking at how Mary was dressed she probably didn't use the front door, walked casually to the elevator (hoping that no one would notice her outfit) and asked Janine to let her in
    – Oliver_C
    Jan 13, 2014 at 22:59
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    Nope. If Janine had let her in, she would have seen her in her 'wetwork' gear. Not to mention as it was Mary who knocked Janine out, and later (in the hospital scene) Janine tells Sherlock to send her love to the Watsons. Its unlikely she would have said so if she had known it was Mary who attacked her... I already thought about this earlier. Jan 14, 2014 at 0:24

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