I have a theory about how John and Henry were affected with the drugs, without being in contact with the fog ( Henry was afraid of the place where his father died and i dont think he spent much time there all the years )
Henry has a lightning installation at his house and in a scene he hallucinate right after the lights turning on. The same thing happened to John in the lab: first It was dark, then the (very bright) lights turning on and he saw what Sherlock wanted him to see.
Dr. Frankland develop his drug further the last 20 Years and maybe thats the result.
I think there must be also something to conduct the light into the Brain, maybe the sugar or the coffee.
Sherlock said to Watson, that he is a good conductor of light or something similar ( i only know the german version, so i hope i use the right words ) maybe as a hint Watson did not understand.
Sherlock did not really  want that anyone understand it elsewise he would explain it to show how great he is. But why? Maybe because he have a mighty weapon now, nobody knows about ( Frankland is dead) to fight against Moriarty
You remember the scene at the Episode "Reichenbach Fall" on the top of the roof before Moriarty shoot Himself? I swear, it was the same bright light turning on and it sounds  like the light installation from Henrys House. The Teaparty before was maybe needed for conducting the light or something like the coffee.

Edit: Something like optogenetics

Last edited by Danielle80 (March 31, 2016 5:05 pm)