Computational film analysis combines statistics, data science, information visualization, and computer science with the analytical approaches and domain knowledge of the study of film to frame and answer questions about form and style in the cinema. In this article I illustrate the visualisation and analysis of the soundtrack of the trailer for the Korean horror film Into the Mirror (2003). Using the spectrogram and normalized aggregated power envelope to show how the sound design of the trailer evolves over time and functions at different scales. I address a range of practical considerations relevant to the methods demonstrated here relating to the use of mono versus stereo audio files, the use of different sampling rates, and audio normalization. A supporting website with the code for the statistical programming language R used in this analysis is available at https://rpubs.com/nr62_rp33/CFA-into-the-mirror.