Here’s a synopsis of a story of which a friend of mine cannot recall the author or title:
The details I remember are sketchy but here is what I have. A man
arrives at a out of the way country house. He meets the young master and is told
that the master will be away much of the time, but that while the man is
there alone he should not try to enter any of the rooms that are locked or remove the coverings from the mirrors of the house. There is a parrot that he is
supposed to be looking after and he ends up putting its cage near one of the
mirrors and a skeletal hand grabs the parrot from through the mirror. Of course he does remove the coverings from some of the mirrors and goes into the locked rooms and the man ends up being chased by whatever this thing in the mirror is. There is a large mirror at the foot of a staircase and the
man sees the thing in the mirror and throws a candelabra at it and shatters
the mirror. The man then finds the dead body of the master lying amongst the shards of the mirror. I also think that this is written in the format of a letter that the man is writing on the night before he is executed for the murder of the young master.
Sound familiar?