In this Swedish horror film, a young boy named Oskar meets his mysterious neighbour Eli, who turns out to be a centuries-old vampire who kills people in order to exist. They develop a twisted romance, and Eli's means of helping Oskar confront his problems are anything but innocent. In fact, it's implied throughout Let the Right One In that Eli is grooming Oskar to be a familiar, that is, a mortal vampire servant.