The film "Letter X" follows a teenage girl named Anabella who begins receiving anonymous letters from one of her ex-boyfriends. However, she does not know which ex is sending the letters as she cut off contact with both after their breakups. Over the course of 8 minutes, Anabella receives more letters and tries to deduce who the sender is based on clues in the letters, but is left confused. In the climax, the last letter contains a phone number and Anabella texts it, receiving a response that reveals the identity of the ex who has been sending the letters all along in an attempt to reconcile.