Lara (Eleanor Tomlinson) and her estranged father, Dr. Hill (Stephen Rea), travel behind the iron curtain to a decrepit castle outside the Hungarian town of Styria. In the nearby woods, Lara witnesses a car crash. Carmilla, (Julia Pietrucha), escapes from the wreckage as a driver attempts to run her over. When Lara hides this beautiful and mysterious stranger in the castle, the two start an intense and chaotic friendship. As their relationship deepens, the young women of Styria begin to go mad. When local girls are found dead from apparent suicides, Lara wonders if Carmilla is to blame or is there a darker secret behind the mass hysteria destroying the town.