3) Mrs. Robinson
This is a visual easter egg in the form of composition. In the beginning of the ep, when we see John talking to a shadowed woman for the first time of many, we are briefly made to think he’s talking to “Elizabeth” until it’s revealed he’s, in fact, speaking to his dead wife.
In that brief moment before Mary is revealed, John is framed in an inverted V made by the form of the woman, and the image’s layout looks exactly like the iconic image from The Graduate (Dustin Hoffman framed by a shapely leg) that it has to be an Easter egg, not a coincidence.
2) The Sign of Four Deductions
Faith Smith’s paper on which she attempted to remember details from her father’s fateful meeting was folded and kept in a pocketbook and then pinned up on a board. These very things are deduced by Holmes in The Sign of Four about the map belong to Mary Morstan’s father that she kept aside. This was, of course, given to Euros by a “mutual friend” of hers and Culverton Smith’s. Speaking of:
1) Euros = The East Wind
Well, now the warning of Mycroft: “The East Wind is coming to get you” becomes much more than a mere childhood tale and reference to canon story “His Last Bow.” Now we get a real feeling of the sinister from this and, holy cow, what is up with Euros Holmes’ powers of infiltration?! And the “miss me?” Is that just her being triggery, or was she at one point working with Moriarty, or what what what???
Oh, yeah, my point: Euros means the east wind. And it is a rather threatening one, if you’re looking at Greek mythology. But then she’s happy to tell us this at the end of the ep. And I am terrified to see if that gun was pointed where it looked like it was, and if it hit….
So what’s up with Sherrinford, then? Many commentators have averred that Sherrinford is Euros’ code name, rather like the code names Lady Smallwood and co. sported at the beginning of “The Six Thatchers”. I tend to agree with this hypothesis as the most likely. How about you?