A mystery was a genre of film in which the central focus of the plot was a criminal act whose nature and/or perpetrator was unclear.
Some people believed that the enjoyment of a mystery film was partly due the audience's attempts to use logical reasoning to solve the mystery before the detective did. In 2153, while T'Pol dreamed she was watching Appointment with Danger on Enterprise NX-01's movie night, Trip Tucker and Doctor Phlox discussed the film's plot loudly in her hearing. When she suggested that they watch the movie rather than converse about it, Tucker shared this belief with her, adding, "You of all people should appreciate that." Despite his reasoning, T'Pol still felt they were speaking too loudly, replying that they ought to "use logic more quietly." (ENT: "Impulse")