Davison, in particular, is on fine form in Black Orchid. Quite topping, one could say. His visible frustration at being lost in the abandoned wing of the house, finding the dead body, then it again when trying to explain it all to Lady Cranleigh is superb.
Trying to get Lady Cranleigh to open up he questions her,
"You remember, the Indian, you said he was a friend, from Brazil..."
Lady Cranleigh pretends not to know anything, "Brazil?" she replies all innocently.
"Yes," sighs the Doctor, as all hope seems to be fading rapidly, "where the nuts come from..." Really beautifully played by Davison.
You have to feel a bit sorry for the partygoers however: the exterior shots look bitterly cold, and the women are all wearing flimsy dresses... The lighting guys do their best to add a bit of sunshine, but they are fighting a losing battle against the Great British Weather and it's impossible to make a damp October day look like a warm summer party!
Black Orchid is also notable for the fact that the TARDIS crew all stick around for the funeral, which must have been a day or so at the very least after the story ostensibly finished. An unusual, but welcome touch.