There will be some mild spoilers. If you haven't seen this movie then make it your duty to do so this and every Halloween.
Dr. Barret his wife and two psychics are tasked to find proof of the afterlife in an old mansion with a deadly reputation during the week of Christmas. That's right, folks. This here is a Christmas movie. The doctor wants to use this opportunity to prove that random psychic energy is to blame for paranormal happenings and not intelligent beings existing just slightly beyond the reach of the living. He has disagreements that get a bit heated towards the end with the lady psychic Florence Tanner to the point she tries to bash his energy eliminator machine on the off chance that he may be right. You have two thoughts on the subject of ghosts and they butt heads with each other from time to time. Both acknowledge the paranormal but one views it in strict scientific terms of energy while the other leans to the spiritual.
THE LEGEND OF HELL HOUSE is in my opinion one of the scariest films ever made. The film stirs the imagination with its bleak gloomy atmosphere, foreboding dark mansion and giant black cat that doesn't seem to want to stay dead. There really is no need for special effects. The movie lets your mind do all the work. I love the idea of two opposing views challenging one another as the group tries to figure out how this home is so haunted. The movie follows the #1 rule for a really good horror movie and that is 'Anyone can die at anytime.' The movie is quiet and solemn luring the audience into a guarded calm that is suddenly shattered when something frightful happens.
Roddy McDowall's character had actually been in the house before being the only survivor of a group investigating the house years before. He keeps a reserved demeanor protecting himself from the psychic energy that is all around him. He comes to life though almost stealing the show when he discovers what is really going on. I love how he figures out that both the doctor and Tanner were right. He challenges the entity exposing it for the small man that is truly behind all the horrors of the house. It is almost like the Wizard behind the curtain in THE WIZARD OF OZ. The large foreboding house and all of it's ghastly fame comes from the insecurity of a small vain dead man.
On Halloween night if you are looking for a scary double feature I would recommend watching this one side by side with the original THE HAUNTING. There is a good story to think about with a solid conclusion. Just don't think too long about it. This one may give you nightmares.