"The Demented" is sort of a reminiscent of a lower-budget version of "28 Days Later". So is that a good thing or a bad thing? Well that depends on what kind of zombies - or infected - you enjoy in movies.
Story-wise, then "The Demented" is a very standard movie as movies go in the zombie genre. A group of young people find themselves trapped in a rural setting when a biological outbreak takes place - turning people into crazed killers. And I would use the term zombie loosely here, as they aren't exactly zombies, if you measure them up by the standard of many movies in the genre.
The infected in the movie, like in "28 Days Later", are agile and fast running. And for some reason they have to make sounds like prowling animals. And also, once you become infected, your clothes become shredded and ripped. Try looking at all the infected, their clothes is all torn and ripped, and they are smeared in blood, yet they don't have any visible cuts, wounds, bite marks and the like. It was a little bit too ridiculous.
The way the movie ended was actually a nice twist to an otherwise generic zombie movie. I will not spoil anything by mentioning it here, but I didn't see that ending coming, not by a long shot.
As for the title of the movie, well, they could have found something more appropriate, as "The Demented" doesn't really do a zombie movie any kind of justice in any possible way.
For a zombie movie, then "The Demented" didn't really bring anything new or innovative to the genre. Everything in the movie has been done or seen before. But still, the movie was enjoyable and actually fared well for a movie of this production value.
