A German crime thriller from the year 1963 and one of the Film/EdgarWallaceFilms.

One night at Blackmoor Castle, a masked man appears before its owner Lucius Clark and demands that he hands over a batch of diamonds he stole some time ago. Clark refuses, and as he tries to sell the diamonds, the masked man hinders the process by killing people around the castle.

!!Examples in this film:

* AmoralAttorney: Tromby.
* AntagonistTitle
* AxCrazy: Anthony, who is ready to kill someone to get the diamonds
* CallingCard: The Strangler leaves the letter M on his victims' foreheads.
* EvilDetectingDog: Castle's dogs start barking when the Strangler is nearby.
* EvilUncle: Defied. When Anthony suggests to Lucius that "an accident" should befall on his niece so they'd get her money, he is enraged and socks Anthony to the jaw.
* HenpeckedHusband: The chief of Scotland Yard.
* MacGuffin: The stolen diamonds.
* OffWithHisHead: The corpse of castle's gardener is found without his head.
* PlayingPossum: The Strangler pretends to be hurt to get the gardener who was sent to take the stolen diamonds to .
%%* RedHerringMole
* RedRightHand: One of Lucius's fingers is missing and the Strangler seems to share this trait.
%%* UsefulNotes/ScotlandYard
* SecretPath: Blackmoor Castle was a long time ago owned by a robber who made lot of secret tunnels within it.
%%* ShootOutTheLock
* TheXOfY