The Spanish Prisoner

 The Spanish Prisoner  is a suspense/crime/mystery film written and directed by David Mamet. It revolves around Joe Ross, a researcher for an unnamed major company who's recently perfected an unspecified process which is worth a great deal of money. While on a business trip in the caribbean, he meets and befriends a wealthy traveller who offers to advise him and help him get a fair share of the profits. Shortly, however, he begins to question his new friend's motives and intentions. As in most Mamet stories, deceptions and cons pile up as both the protagonist and the audience try to figure out who's telling the truth, and who's part of a plot.

This film provides examples of the following tropes:

 * Chekhov's Gunman:
 * Chekhov's Caugh: Joe's best friend, a lawyer, gets a cold that follows him throughout the movie. Subverted when
 * The Con: Joe spends the whole film trying to figure out what con he's been a victim of. The titular "Spanish Prisoner" con is but one of many.
 * Didn't See That Coming: Almost everything that happened was planned out, but the plotters didn't predict that
 * The Ending Changes Everything:
 * Foreshadowing: Early on, Joe sees a boat moving from a seaplane towards the shore. Susan points out that he never actually saw the boat leave the plane, it could have been coming from anywhere "and we have no idea who anyone is."
 * It Was Here I Swear:
 * Massive Multiplayer Scam
 * McGuffin: The "process", about which we are told absolutely nothing except that it's worth a lot of money.
 * Meta Twist: Mamet must have known that the audience would be expecting a con game to turn up in this film. We hit that twist and the con is uncovered and explained before the movie is half over. Then we realize that we haven't uncovered anything yet.
 * Police Are Useless:
 * In fairness to the police, things were deliberately set up so that Joe would look guilty and half of his story fell apart on inspection. Naturally they don't believe his pleas of innocence.
 * Out Gambitted: The plotters had a brilliantly detailed and multi-layered plan to get ahold of the process and leave Joe to take the fall. In the end
 * Undercover Cop Reveal:
 * Undercover Cop Reveal: