he sees that his forehead is dirty. But in previous scene it was not! and where did it got dirty from?
If his forehead was not dirty in the previous scene, that is a mistake that should be added to the IMDB goofs.
His forehead was dirty from soot that fell from the chimney when he shoved the umbrella up inside.
It didn't occur to me till the last time I saw it (less than a week ago), but showing a smudge on his forehead TWICE sounds like they were "riffing" on Macbeth, where Lady Macbeth can't seem to lose the spot on her hand. Maybe I'm all wrong about that, but if I'm not, it would be a second episode with a Macbeth connection, after Dagger of the Mind.
I always thought he smeared the soot on his forehead from his handkerchief, which got dirty earlier. But I could be misremembering the scene...
It rained in Dagger of the mind
I recently watched an episode of the British crime series "Father Brown" which features a crime solving Catholic priest in a small English village in the late 1940s, early 1950s.
In this episode the supposed murder victim had actually framed someone by committing suicide. The method? Tieing the gun to a large stone and dangling the rope down the chimney. After the victim fired the gun he let go of it and the weight of the stone slid down the roof above pulling the weapon up the chimney. The stone and rope were obscured by the angle of the roof.
I thought to myself, where have I heard that idea before?
It's from Sherlock Holmes." The ____...Bridge"
Well indeed, so it is.
Every day is a learning day as the saying goes.