Eurus is Sherlock
I know this idea has come up more than once. In this post I will try to collect as much evidence, mostly from TFP, as possible - visual, textual, and narrational.
In this first scene together their hands seem to melt into each other. Sherlock does not expect to be able to touch his sister, and then their fingers interlace just like that. In the second picture both have become one. Sherlock is shining through Eurus’s reflection, her hear roughly being place where his heart is (head/brain and heart becoming one).
Additional note: If we assume that this is her real hair as opposed to the wigs she wore in TST and TLD, they both have dark curly hair.
- Sherlock and Eurus are very close in age. True, it’s never twins. But at least Irish twins, it seems. (Or just one person after all?)
- Sherlock has been deemed a genius from the beginning. Eurus “was described as an era-defining genius, beyond Newton.”
- Both play the violin. Eurus even plays a Stradivarius as does Holmes in ACD Canon.
- Sherlock had no friends before John. “I had no one.”
- Both love to be dramatic.
- Both are prone to violence: Sherlock torturing the cabbie / throwing a man out the window / shooting Magnussen. / Eurus’s violent behaviour in TLD and TFP.
- Both are seen in a cell of some kind: the padded cell in Sherlock’s HLV mind palace / the Sherrinford cell (All places from the HLV mind palace have real counterparts - so what about the cell? And how probable is it that two siblings both have been inmates of a cell in a mental hospital/prison at some time?)
- Both are in a way attracted to Moriarty and are willing to play games with him.
- Both are given delicate tasks/cases by Mycroft that concern state security (the Bruce-Partington plans/Irene Adler/the Parliament bombing in TEH/the planned terrorist attacks mentioned in TFP).
- Sherlock experiments on John in ThoB. Eurus experiments on Sherlock in TFP.
- Both are very focussed on knowledge: “I don’t like not knowing.” / “She knew things she should never have known …”
- Both are disguising themselves / hiding in plain sight.
- Both are being used by Mycroft for matters of state security and intelligence.
- Both are believed to be dead for years. Both times Mycroft is involved in the plots to fake their deaths.
- “She was different from the beginning.”/”Because he attacks people who are different and preys on their secrets.” (Why Sherlock hates Magnussen)
- “Listen. This is my hard drive and it only makes sense to put things in there that are useful.” / “I remember everything; every single thing. You just need a big enough hard drive.”
- Sherlock being involved in the flight of the dead/saving Irene from terrorists/revealing the terrorist plot in TEH / “She predicted the exact dates of the last three terrorist attacks on the British mainland after an hour on Twitter.”
- “In any event, there is no prison in which we could incarcerate Sherlock without causing a riot on a daily basis.” / “The depth of Eurus’s psychosis and the extent of her abilities couldn’t hope to be contained in any ordinary institution.“
- “That in your case, solitary confinement is locking you up with your worst enemy.” This can also be applied to Eurus’s imprisonment in Sherrinford.
These are a lot of similarities. Too much for coincidence, if you ask me. To me, Eurus is an exaggerated, overdramatic version of Sherlock himself. What he could have become without John’s friendship and Mycroft’s support, without the friends he has found quite late in life.
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