Rebecca, a young girl haunted by her father's suicide, begins her junior year at an elite girls boarding school, hoping for a fresh start. From the outset, her friendship with sunny, innocent Lucy is shattered by the arrival of Ernessa, a mysterious, dark and beautiful girl from Europe. As Ernessa consumes more and more of Lucy's attention, the latter’s healthy young body grows pale, thin and weak - as if being drained of life itself. Her friendship with Lucy slipping away, Rebecca develops a crush on her handsome English professor, Mr Davies, who is teaching a course on supernatural literature. Obsessed with “Carmilla”, the vampire story that inspired Bram Stoker’s “Dracula”, she grows increasingly suspicious of Ernessa's odd behavior and Lucy's wasting illness, and when mysterious deaths shock the school, becomes convinced that Ernessa is a vampire. Rebecca finds herself isolated when the other girls dismiss her suspicions as mere jealousy and Mr. Davies betrays her trust. As Lucy's inexplicable illness turns deadly, Rebecca is left alone to battle with Ernessa for the life of her friend.
The supernatural elements in “The Moth Diaries” are rooted in the real experience of a young girl faced with her emerging sexuality and caught in a web of obsessive friendship, jealousy and betrayal. A powerful emotional drama where eroticism and death are entwined