The Moth Diaries is a 2011 Gothic horror film written and directed by Mary Harron, based on the 2002 novel of the same name by Rachel Klein. The film stars Lily Cole, Sarah Gadon, Sarah Bolger, Judy Parfitt, and Scott Speedman. The plot follows Rebecca, a teenage girl who suspects that Ernessa, the new student at an all-girls boarding school is a vampire. An Irish-Canadian venture, the film was co-produced by Samson Films and Mediamax.