Reverse chronology is a method of story-telling whereby the plot is revealed in reverse order.
In a story employing this technique, the first scene shown is actually the conclusion to the plot. Once that scene ends, the penultimate scene is shown, and so on, so that the final scene the viewer sees is the first chronologically.
Many stories employ flashback, showing prior events, but whereas the scene order of most conventional films is A-B-C-etc., a film in reverse chronology goes Z-Y-X-etc.
As a hypothetical example, if the fairy tale Jack and the Beanstalk was told using reverse chronology, the opening scene would depict Jack chopping the beanstalk down and killing the giant. The next scene would feature Jack being discovered by the giant and climbing down the beanstalk in fear of his life. Later, we would see Jack running into the man with the infamous magic beans, then, at the end of the film, being sent off by his mother to sell the cow.
The unusual nature of this method means it is only used in stories of a specific nature. For example, Memento features a man with anterograde amnesia, meaning he is unable to form new memories. The film parallels the protagonist's perspective by unfolding in reverse chronological order, leaving the audience as ignorant of the events that occurred prior to each scene (which, played in reverse chronological order, will not be revealed until later) as the protagonist is.
In the film Irréversible, an act of homicidal violence takes place at the start of the movie (i.e. it is the final event to take place). During the remainder of the film we learn not only that the violence is an act of vengeance, but what exactly is being avenged. The film was highly controversial for its graphic nature; had the scenes been shown in chronological order, this violent content would make it a simple, and pointlessly brutal, revenge movie. However, as it is, told in reverse, the audience is made to consider the exact consequences of each action, and there is often 'more than meets the eye'.
The epic poem Aeneid, written by Virgil in the 1st century BC, uses reverse chronology within scenes. In "The Three Apples", a murder mystery in the One Thousand and One Nights, the middle part of the story shows a flashback of events leading up to the discovery of a dead body at the beginning of the story. The action of W. R. Burnett's novel, Goodbye to the Past (1934), moves continually from 1929 to 1873.Edward Lewis Wallant uses flashbacks in reverse chronology in The Human Season (1960). The pessimistic masterpiece Christopher Homm (1965), a novel by C. H. Sisson, is also told in reverse chronology.