***SPOILERS*** German movie about a masked killer in and around the English castle of Blackmoor who's out to avenge his fathers murder by the future Lord Lucius Clark, Rudolf Fernan, who lives there.
The killer who's father Charles Manning was Clark's assistant and good friend in the British colony of Kimberly in Africa, where Clark was the district governor, was murdered by Clark who stole over 6 million in pound sterling worth of uncut diamonds that his father had. What the killer doesn't seem to know is that Clark is really his father, which was brought out at the end of the movie. But there seems to be some disconnect here with the killer when it's revealed that he came upon a batch of love letters by Clark to his mother Bettie Manning that he found hidden in the castle! the guy couldn't put two and two together?
Early in the movie we see that Clark is having the stolen diamonds cut by his creepy butler Anthony, Dieter Eppier, who used to be an expert diamond cutter until he was sent up the river for five years for stealing diamonds from his employer. Clark is secretly sending the diamonds hidden in cigar tubes to the owner of the "Old Scavenger Inn" in London Mr. Travish, Hands Nielson, who's fencing the hot diamonds by paying Clark in cash for them.
What both Clark and Travish as well as Clark's lawyer Mr. Tromby, Richard Haussler, doesn't know is that the killer has someone working at the "Old Scavenger Inn", his wife, who's tipping him off about the transactions. At one point in the movie he ambushes Clark's delivery man with the diamonds who happens to be his gardener Sebastian, Albert Bessler, killing him and taking the stones.
What the cagey Clark is doing is getting rid of the diamonds so that the killer can't get his hands on them and giving the money that he gets from Travish to his niece Claridge Dorsett, Karin Dor, as stated in his will on or after her 21th birthday. The masked killer is determined to get the diamonds or the money that Clark gets for fencing them before she does even if it kills her.
Interesting German 1963 import that has you guessing to who the killer is until he's dredged out of the swamp outside Blackmoor Castle at the end of the movie and his identity reveled. "Strangler of Blackmoor Castle" is a bit too violent for movies released back then in those days in the early 1960's with a number of shocking and bloody decapitations that are really gruesome even watching the movie now.
The film does have some comic relief in it with the lord of the castle Lord Blackmoor, Hans Reiser, spending all his time listening and recording on his portable tape recorder bird love calls in the woods.
