The world may seem like it's controlled by powerful, invisible, malevolent forces. Much of this impression may be mere paranoia, so the best answer is investigation and illumination. This is what Peter Cushing believes in 1965's The Skull, a simple but pleasantly garish horror film directed by Freddie Francis based on a story by Robert Bloch.
It may come as no surprise that eventually Christopher Maitland (Cushing) bites off more than he can chew in the form of a skull, supposedly the skull of the Marquis de Sade. The filmmakers don't seem particularly interested in the particulars of De Sade's life beyond the fact that his name is the origin of the word sadism. So the skull is cursed, possessed by a demon that makes its owners commit murder.
Cushing is a collector of bizarre, demoniac paraphernalia from all over the world, surrounding himself with these items and books about them in his study where he spends most of his time alone with the things. Naturally, he neglects his wife (Jill Bennett) in the process.
When a dealer (Patrick Wymark) from whom Christopher purchases many objects stops by, she pleads with Christopher to give up his obsession. She's worried he's tampering with dangerous forces. He smiles indulgently and patiently explains, "It's because people, all through the ages, have been influenced and terrorised by these things that I carry out research to try and find the reasons why."
We frequently see Christopher at ease in his study, relaxing amidst his nightmare sculptures, completely assured of his control. With the introduction of the skull, this sense of control is undermined in different ways. In a possible hallucination, he's dragged out of his study by two men who claim to be police and taken to a place where he's forced to undergo some simple, sadistic trials.
This movie mostly works on atmosphere and performances. In addition to Cushing, Wymark is great as his shady dealer and Patrick Magee is memorable in two brief appearances as a police surgeon. But next to Cushing, of course, Christopher Lee makes the biggest impression, despite being only credited as "guest star"--he's actually pretty prominent in the film as the former owner of the skull who cautions his friend to stay away from it. It's just great watching these two talk about this while playing billiards. I could listen to them discuss occult artefacts while playing and drink cognac all night.