"I don't know if I'm innocent of guilt or guilty of innocence." -- Odette
Magistrate Simon Cordier (Vincent Price) speaks to a condemned murderer, Louis Girot (Harvey Stephens), in his cell, wherein Girot says he only killed people because he was possessed by a spirit called a Horla. Cordier learns to his dismay that Girot was telling the truth, when said Horla reveals its presence and its terrible intentions. Cordier, who mourns his wife and child, falls for a very pretty model named Odette (Nancy Kovack), who already has a husband in poor painter Paul (Chris Warfield). A sculpted bust that Cordier makes of Odette is later used for a very grisly purpose. Loosely based on stories by Guy de Maupassant, Diary of a Madman has an excellent story and features a wonderful performance by Nancy Kovack -- its main problem is Vincent Price, who offers his customary charm but otherwise walks through the movie and its horrific events as if all he were thinking of was using his paycheck to acquire more artwork, which was probably the case. Cordier is a terrific role for any actor, but almost always Price just goes through the motions, maintaining that certain image that, unfortunately, often undermined his thesping. Most of the other actors, however, including Ian Wolfe [Games] as Simon's butler, are more on the mark. Price does not ruin the film's entertainment value, but he was more than capable of being so much better if director Le Borg had insisted upon it.
Verdict: Creditable horror flick. ***.