Let The Right One In (2008)

When Oskar (Kåre Hedebrant), a sensitive, bullied 12-year-old boy living with his mother in suburban Sweden, meets his new neighbor, the mysterious and moody Eli (Lina Leandersson), they strike up a friendship. Initially reserved with each other, Oskar and Eli slowly form a close bond, but it soon becomes apparent that she is no ordinary young girl. Eventually, Eli shares her dark, macabre secret with Oskar, revealing her connection to a string of bloody local murders.