I just noticed this:

Mrs Hudson: Look at him, dashing about. My husband was just the same.

The first time I saw this, I understood her saying: Oh, that dashing about behaviour, I know it well, my husband was just like that. Which is slightly ominous, since we found out mere moments before that her husband was put to death in Florida (to her great relief). 

But now I realize that’s not what she’s saying at all.

She doesn’t say: “My husband was just the same,” she says, “My husband was just the same.”

She’s saying, my husband and your boyfriend are quite similar, John! I’m sure we have lots more in common! Let me go get you a cup of tea and we can dish about the men in our lives, shall I?

Ironically all John is thinking at this moment is: I WANNA GO I WANNA GO I WANNA GO TOO THIS ISN’T FAIR SHERLOCK IS SO EXCITING I WANNA SEE THE DEAD LADY TOO OMG TAKE ME WITH YOU SHERLOCK TAKE ME TOO