Narrative

Structure, Formulas and Devices
E.g. Automatic use of 'continuity editing'.
The clear establishment of 'cause and effect' plotting which establishes character motivations and helps tell an interesting story which proceeds logically and steadily.

Enigma's
This refers to a puzzle, something mysterious or inexplicable, or a riddle or difficult problem.
In thrillers this is commonly something which the protagonist has to try to find out or solve before the narrative is resolved and the film finishes.