After a funeral, a group of people assemble to hear the departed last wish, to have his diary read. It reveals a dark tale as Magistrate Cordier (Price) is possessed by a dark force called the Horla which led him to commit terrible crimes. A respectable man, Cordier is possessed after visiting a condemned prisoner. It begins a tragic chain of events as he falls in love with a model Odette (Nancy Kovack), though the fact she is already married to an artist (Chris Warfield) is a complication.
Possessed by the dark force, Cordier kills Odette with the husband ending up condemned for the crime. Cordier knows he must take desperate measures to stop the evil...
A very well constructed horror with a story that builds and builds. It has a number of creepy and supernatural scenes though it is the psychological aspects of the film that are to the fore and really elevate this into something special.
