Sex, blood, and death are the three elements present in every vampire story, or so explains Mr. Davies (Scott Speedman), the hunky English teacher at the Brangwyn boarding school and the only male character seen outside of flashback or fantasy in Mary Harron's The Moth Diaries. Harron's film, which takes place almost entirely within the creepy confines of the hotel turned girl's high school, and which is heavily steeped in the conventions of the vampire narrative (even as it attempts to subvert them), features no shortage of blood and death. But like many a bloodsucker tale, the sexuality is largely repressed, finding its expression in—real or imagined—vampiric activity.
That both the vampire and her victims are all girls adds a decidedly lesbian twist to the narrative, commenting on Davies's further contention that Dracula is primarily about the fear of female sexuality. In establishing the setting and characters, Harron, adapting Rachel Klein's novel, quickly stakes out her own atmosphere of Gothic foreboding (largely thanks to the cavernous turn-of-the-century building where the film takes place), a deep immersion in vampire lore (the students read not only Dracula, but Sheridan Le Fanu's classic tale of the undead, Camilla), and a repressed lesbianism. This last element is downplayed by Harron, but it's present in the girl's reaction to the matronly "dykes" who enforce the dorm rules with an iron fist, in the giddy bedroom parties the students stage, and, after the wan, mysterious vamp Ernessa (Lily Cole) joins the school, in the semi-romantic geometry that develops.
The central triangle of friendship and/or sexuality involves the lead character, Rebecca (Sarah Bolger), losing the attention of her bestie and object of subdued hero worship, Lucie (Sarah Gadon), to Ernessa, who holds sway over Lucie with a sort of supernatural power. Or so it seems to Rebecca, who, alone among the student body, believes Ernessa to be a vicious bloodsucker intent on destroying Lucie. Reality isn't always easy to determine in Harron's tricky film, as Rebecca is often given to fantasies (possibly including the film's one outright instance of lesbian activity), but the film shows us enough material that can be taken objectively, to give credence to Rebecca's theories.
Eventually, things begin to heat up and, as more and more of Rebecca's friends either die or get expelled from class (all, according to our protagonist, Ernessa's handiwork), Rebecca makes a desperate attempt to save Lucie from her seductresses' clutches. Only then does the doubling of Rebecca and Ernessa—both have fathers who committed suicide, both are drawn to Lucie—begin to make sense, as the two come together to realize their bloody, final destiny.
But by this point, most of the film's interest, generated not so much by the is-Ernessa-a-vampire-or-is-Rebecca-imagining-it ambiguity, but by the updating of the sexual tensions present in the classic bloodsucker novel, has been abandoned. Instead, we just get the inevitable de-sexualized showdown between "hero" and "villain," which, while realized with some memorable imagery (a fantasy of bloody rain in the school library), isn't nearly as compelling as many of the film's earlier moments. There will be blood in the end, and there will be death, and fire to boot, but without the third element in Mr. Davies equation, this is one vampire film whose sexless, generic ending betrays a promise of revisionist complexity.