Has anyone else picked up on the “John, rhododendron ponticum. It matches.” moment? The flower is completely irrelevant to the Hansel and Gretel case, yet he makes a point to show this flower to John.
Because I think that’s Sherlock’s sign to John about post-Reichenbach.
Rhododendron ponticum, according to Wikipedia, has a “range [that] includes Spain, northern Portugal, Great Britain, Ireland and southeast Bulgaria, which is the last surviving European Tertiary habitat.”
More importantly, “Honey produced with pollen from the flowers of this plant can be quite poisonous, causing severe hypotension and bradycardia in humans if consumed in sufficient quantities, due to toxic diterpenes (Grayanotoxins)”
Hypotension is severely low blood pressure, combined with bradycaria, which is a condition/state in which the heartrate is below the usual 60bpm, both of which can aide in mimicking death (in other words, paralysis).
The only issue is: how did he get the drug? How long does it take for it to go into effect? Or does the rhododendron point to something other than poison (a code or location)? Either way, I think is a clue of some sort. (Also, I believe this flower was used in the other Sherlock Holmes movie, but hey, nothing is as it seems on this show. I bring this up as a start, not an end)