Once Upon a Thriller is the fourth book in the Nancy Drew Diaries series. Nancy Drew and her friends are enjoying a trip to an exclusive movie studio where an upcoming blockbuster film, based on a dark fairy tale, is being filmed. The set should be a dream, but instead, it becomes a nightmare when a series of accidents, strange occurrences, and threats begin plaguing the production. It quickly becomes clear that someone is trying to shut down the film, possibly using the film's own script as a blueprint for chaos. Nancy must use her sharp observation skills to examine the elaborate set, question the highly temperamental cast and crew, and decipher the cryptic clues to unmask the perpetrator before the final scene is ruined.
