Sherlock Season 4: 9 Big Questions After 'The Lying Detective' 

6. How Did Sherlock Not Recognise His Own Sister?

Sherlock Lying Detective Questions
BBC

While Watson's therapist doesn't reveal herself to be Sherlock's sister until the end of the episode, the detective himself does unknowingly spend a fair bit of time with her during it.

Again, she's in disguise, but does that really explain how Sherlock - the world's greatest detective - can't figure it out. Another explanation might be that it's because of his drug-addled state, but again, it's a little hard to buy given she's staring him in the face.

Does that mean, then, he doesn't even know she exists, or at least hasn't seen her since they were children?

Contributor
Contributor

NCTJ-qualified journalist. Most definitely not a racing driver. Drink too much tea; eat too much peanut butter; watch too much TV. Sadly only the latter paying off so far. A mix of wise-old man in a young man's body with a child-like wonder about him and a great otherworldly sensibility.