A couple of sniveling teenage cretins are rooting around an old abandoned mental hospital when they find something rather disturbing: a young woman strapped to a gurney, seemingly abandoned. One of the creeps wants to contact the authorities, but the other talks him out of it. Instead, creep #2 uses the girl as his sex slave, eventually inviting other people from high school to join in. Here's the thing though, this isn't any ordinary girl, she's some sort of zombie beast with the requisite taste for human flesh.
Whatever potential Deadgirl had is squandered by a screenplay that, despite some interesting ideas, is poorly written, has no sense of direction, and is maybe a little dishonest. The filmmaking struck me as competent, effectively establishing atmosphere here and there, and the acting was uniformly strong given the material. But from pretty early on you know the script is bullshit, not really interested in exploring the ideas it presents so much as using them for shock effect, inevitably copping out on dealing with their implications.
For instance, I'll buy the central premise that some sociopathic creep would rape a girl he finds tied up and keep her hidden. Theoretically, its an effective idea for a disturbing movie. But the two leads, who are only supposed to be teenagers, under-react to finding the girl, and one of them already begins to suggest rape within a few spare minutes. There's no build to it, they don't panic or try to untie her or have a long argument. The movie isn't interested in wondering why some sick fuck would want to do awful shit like this, it just wants to skip right ahead to the awful shit.
Making the girl into some sort of zombie is an evasion. It shifts the movie from a psychological thriller about vicious, sociopathic tendancies in teenage boys into a run-of-the-mill zombie movie. It aims to shock by posing the question "is an average teenager capable of something this heinous?", then it promptly ignores the question once it achieves the desired effect. In my book, you don't get to do that. You either make the disturbing, cynical psychological drama your premise implies, or you leave those toys in the toy box for the big kids to play with.
Don't get me wrong, this is not a terrible movie. The villain's performance gets under your skin, there is occassionally some effective dark humor, and a handful of effective sequences. If I'm being extra negative about Deadgirl, it's because it seemed on the verge of being good, but never made it there.