The Strangler of Blackmoor Castle

Rating:
Summary: Can you guess who the Strangler is?
Review: German film, dubbed in English.
An elegant dinner party, in honor of the Queen, bestows the Blackmoor Castle. Meanwhile, the dogs that are inside their pen outside are barking wild. The overseer tries to calm the dogs when suddenly a black-hooded strangler kills the first victim.
With the dinner party over and a success, the house is now empty to Lucius Clark, the host of the party. Just then, he is assaulted by the Strangler phantom who demands Clark to give him the uncut diamonds that belonged to the victim, Charles. Lucius Clark denies he has the diamonds. So the phantom warnes him, he shall make his life a hell on Earth. And furthermore, he doesn't show his face because he has many faces. Lucius Clark is not to leave Blackmoor Castle. The phantom is startled by the noise of another person coming in and escapes outside and runs through the garden.
The Strangler of Blackmoor Castle is still lurking and killing.
Can you guess who the Strangler is?