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Night of the Living Dead was a turning point in zombie film history, influencing the genre in a permanent way and unfortunately inspiring several horrible imitations. Up until this point, most zombie films portrayed zombies as being created by someone for some nefarious purpose. In this film, written and directed by George Romero, the zombies are created by accident, serving nothing but their own savage instincts. (John A. Russo was a co-writer, but given what I've seen of his other films, I don't think he really had much input here.) Romero also established the idea that being a zombie was communicable. In this film, this is merely because if you are dead, whether killed by a zombie or not, you are going to rise. This evolved in later films to zombieism being some kind of disease, where even if you are just bitten, you can turn. At any rate, this type of zombie dominated the zombie film genre thereafter.
In the movie, radiation causes the dead to rise from their graves and pursue the living. A group of strangers is trapped inside a farmhouse, and as they fight to keep the zombies out and stay alive, they are also fighting with each other on the best way to go about it. This is one of the great characteristics of Romero's films, that the protagonists are all too human and must often overcome adversity within their own group as well as from the zombies.
This film is well-written and acted, and the effects are good without being over-the-top gory. Romero keeps things tense as the two main human rivals in the film, Ben (Duane Jones) and Harry (Karl Hardman), argue about the best strategy, while the zombies outside the farmhouse keep gathering. Excellent film.