Here is the scene of The Fall I am talking about. It's from the first episode in the first season, in fact within the first ten minutes actually.
Here the character pulls of a mask and the camera is in first person POV. So, the mask is shown to be pulled off from the camera.
But in the mirror, it is shown that the character is actually pulling the mask off.
How did they shoot the scene? Is the mirror just a glass separating two identically arranged room?