Question: What literary technique that introduces a radical change in the direction or expected outcome of the plot is the play "Mousetrap" known for using?

Context paragraphs:
Frame story: A frame story (also known as a frame tale or frame narrative) is a literary technique that sometimes serves as a companion piece to a story within a story, whereby an introductory or main narrative is presented, at least in part, for the purpose of setting the stage either for a more emphasized second narrative or for a set of shorter stories.  The frame story leads readers from a first story into another, smaller one (or several ones) within it.  The frame story may also be used to allow readers to understand a part of the story, then jump to another part that can now be understood.  This is not however, to be mixed up with a narrative structure or character personality change.

List of narrative techniques: A narrative technique, also known, more narrowly for literary fictional narratives, as a literary technique, literary device, or fictional device, is any of several specific methods the creator of a narrative uses to convey what they want—in other words, a strategy used in the making of a narrative to relay information to the audience and, particularly, to "develop" the narrative, usually in order to make it more complete, complicated, or interesting.  Literary techniques are distinguished from literary elements, which exist inherently in works of writing.

Plot twist: A plot twist is a literary technique, introducing a radical change in the direction or expected outcome of the plot in a work of fiction.  When it happens near the end of a story, it is known as a twist or surprise ending.  It may change the audience's perception of the preceding events, or introduce a new conflict that places it in a different context.  A plot twist may be foreshadowed, to prepare the audience to accept it.  There are a variety of methods used to execute a plot twist, such as withholding information from the audience, or misleading them with ambiguous or false information.

The Good Soldier: The Good Soldier: A Tale of Passion is a 1915 novel by English novelist Ford Madox Ford.  It is set just before World War I and chronicles the tragedy of Edward Ashburnham, the soldier to whom the title refers, and his own seemingly perfect marriage and that of two American friends.  The novel is told using a series of flashbacks in non-chronological order, a literary technique that formed part of Ford's pioneering view of literary impressionism.  Ford employs the device of the unreliable narrator to great effect as the main character gradually reveals a version of events that is quite different from what the introduction leads the reader to believe.  The novel was loosely based on two incidents of adultery and on Ford's messy personal life.

The Mousetrap: The Mousetrap is a murder mystery play by Agatha Christie.  "The Mousetrap" opened in London's West End in 1952, and has been running continuously since then.  The longest running West End show, it has by far the longest initial run of any play in history, with its 25,000th performance taking place on 18 November 2012.  The play is known for its twist ending, which the audience are traditionally asked not to reveal after leaving the theatre.

Gumption trap: A gumption trap is an event or mindset that can cause a person to lose enthusiasm and become discouraged from starting or continuing a project.  The word "gumption" denotes a combination of commonsense, shrewdness, and a sense of initiative.  Although the last of these traits is the primary victim of the "gumption trap," the first two suffer indirectly in that a reduction in initiative results in a reduction in constructive activity and therefore inhibits one's development of the first two traits.  The "trap" portion of the term refers to the negative feedback loop that the event or mindset creates: That the reduction in the person's enthusiasm and initiative decreases both the person's likelihood of success in that project and the degree of success likely (thus doubly affecting the expected outcome of the person's efforts).  The usual result, whether a mere lack of success or instead an outright failure complete with embarrassment and loss of the resources initially invested, further discourages the person.

Effectiveness: Effectiveness is the capability of producing a desired result or the ability to produce desired output.  When something is deemed effective, it means it has an intended or expected outcome, or produces a deep, vivid impression.

Rational agent: In economics, game theory, decision theory, and artificial intelligence, a rational agent is an agent that has clear preferences, models uncertainty via expected values of variables or functions of variables, and always chooses to perform the action with the optimal expected outcome for itself from among all feasible actions.  A rational agent can be anything that makes decisions, typically a person, firm, machine, or software.

Partners for Change Outcome Management System: The Partners for Change Outcome Management System (PCOMS) is a behavioral health outcomes management system for counseling and therapy services, developed by Barry Duncan and Scott Miller.  The approach was inspired by Michael J. Lambert’s research regarding the use of consumer feedback during the therapeutic process with the Outcome Questionnaire 45.2 (OQ) and is designed to be a briefer method to measure therapeutic outcome.  PCOMS employs two brief, 4-item scales, the Outcome Rating Scale (ORS) and Session Rating Scale (SRS).  The ORS is designed to monitor therapeutic outcome and is given to the client at the beginning of each counseling session.  The ORS focuses on what has happened for the client between sessions and provides an early warning system for clients at risk for a negative outcome.  The results are discussed in a transparent manner to promote collaboration between the client and therapist in planning the next step especially when there is no progress.  The second form, the SRS, monitors how the session has gone for the client, and is given at the end of each therapy session.  The SRS is designed to measure the therapeutic alliance given its importance in leading to positive treatment outcome Using PCOMS in clinical practice has been shown to result in a three and a half times more likelihood of achieving reliable change and half the likelihood of deterioration during treatment services.  PCOMS is part of a growing trend in psychotherapy towards monitoring and managing clinical outcomes and is only one of two systems (the other is the OQ 45.2) with randomized clinical trial support.

List of James Bond gadgets: This is a list of James Bond gadgets featured in the Bond films.  The James Bond books and films have featured exotic equipment and vehicles, which often prove to be critically useful.  The original books and early adaptations had only relatively minimal pieces like the modified attache case in "From Russia, with Love".  However, the gadgets took on a more spectacular profile in the film version of "Goldfinger", and its tremendous success encouraged the following films to have Bond supplied with still more equipment.  For instance, it became an expected scene in each film where Q would present and demonstrate Bond's assigned tools for the mission, and it was a near guarantee that each and every piece would be invaluable to Bond in the field.  In this sense, Bond gadgets became a prime example of the literary technique of Chekhov's gun.

Supporting paragraphs: The Mousetrap Plot twist
Answer: plot twist