Narrative - structure, formulas and devices.

The clear establishment of 'cause and effect' plotting which establishes character motivations and helps tell an interesting story whcih proceeds logically and steadily.

Enigmas:
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.

Red herrings:
A red herring is the name given to a divice which intends to divert the audience from the truth or an item of significance. Can work with other devices (enigmas) to create suspense.

Example - in saw two charaters spend time imprisoned in a room in which a third character lies dead. Throughout the film, both characters appear to be guilty of a series of murders, until it is discovered at the end that the third person in the room is not actually dead but is the killer.