It takes a while for Tobe Hooper’s original The Texas Chain Saw Massacre to get to the terror and gore that it’s so notorious for. The first half hour of the film is just about a group of youngsters driving to a deserted farmhouse where they plan to get up to who knows what adolescent naughtiness. Making out? Smoking dope? It doesn’t really matter because their plans for a good time are skuppered when one of the boys enters a neighbouring house and never comes out.

The house in question is occupied by a chainsaw-wielding psychopath called Leatherface, his two brothers and their grandfather. This family takes dysfunction to a whole new level. They rob graves and kill people, then decorate themselves and their home with bones, skin and other grisly human remains. Better Homes magazine would not approve! And the eldest brother -- known as The Cook -- prepares meals from what can only be assumed is human meat.

When the teenagers start entering the house of horror one by one to look for their missing friend, all hell breaks loose. Leatherface kills and butchers each of them until finally only one of the group, a girl called Sally (Marilyn Burns), remains  alive. The rest of the film shows how Sally faces cruel and sadistic torture from Leatherface and his weirdo family. The horror in these scenes is very effective because Sally’s screams sound so terrifyingly real. If ever there was an actress whose screams could encapsulate sheer terror and fear of death, it's Marilyn Burns.

What makes Leatherface one of horror cinema’s most famous scary killers is that he's such an inarticulate brute. Without saying a word, he will keep coming after you with whatever weapon he can lay his hands on until he has cut you into pieces. He certainly doesn’t make small talk about art and literature like Hannibal Lecter. His only interest is to torture and kill. The film’s very last shot, of Leatherface maniacally waving his chainsaw at the setting sun, emerges as one of the most iconic moments in the entire horror genre and has the power to send shivers up and down your spine with every viewing.

The film opens with a note claiming that it is based on a true story. The case that inspired it is that of Ed Gein, who killed two women and robbed several graves, then decorated his home with the body parts. However, the film’s title is a complete fiction because Gein did not use a chainsaw, there was no massacre -- and he lived in Wisconsin, not Texas.

No other serial killer probably inspired as many films as Ed Gein. Apart from The Texas Chain Saw Massacre, other films that have “borrowed” details from the case include the movie's three sequels, the 2003 remake, Alfred Hitchcock’s Psycho and the Buffalo Bill character in The Silence of the Lambs.

If Gein’s real-life victims endured anywhere near the level of misery and suffering depicted in The Texas Chain Saw Massacre, then the film is exploitation of the worst kind. As a portrait of how low and depraved human beings (whether they’re hillbilly cannibals or 1970’s filmmakers) can be, this horror movie is chillingly effective.

(Released by New Line Cinema; rated "R" for extreme violence and gore.)