'Diary of a Madman' (1967) -  Reginald Le Borg. 

Wonderful Gothic melodrama directed with considerable flair by the delightfully monikered Reginald Le Borg (now there's a name entirely suited to the genre!). Like many early forays into Freudian horror, the premise is a somewhat whimsical affair; in this instance the film posits the idea that pure evil exists as a separate, sentient entity, more than ready, willing and able to sinisterly commandeer the mutable mind of man for its own malevolent end! This ersatz poltergeist (The Horla) eventually takes malignant hold of the noble and law-abiding mind of Magistrate Simon Cordier(Vincent Price) This mercurial actor has a seemingly effortless facility to play flawlessly fascinating aristocratic crazies! This dreadful phantasm then proceeds to ignominiously drag this once erudite magistrate into the degenerate realms of a gibbering bedlamite! 'Diary of A Madman' is an entirely splendid, neatly wrought horror tale with yet another sterling, full-bloodied Price performance to recommend it. This splendidly rousing, madness arousing Guy De Maupassant adaptation is a worthy compliment to the similarly pitched, unrepentantly Gothic, vividly colourful Corman/Poe pot boilers from the same era.