Almost all stories depend upon uncovering information that is hidden in some way. The obvious example is when the killer is revealed in a mystery story. In a single moment, the pieces come together for the reader, the detective demonstrates his or her brilliance, the culprit get the blame, and the innocent suspects are let off the hook. (A few readers may have guessed who the killer is before the reveal, but, we hope, not by too much.)
Of course, if it is not done well, the pieces might not come together or the answer might be so obvious it is disappointing. A revelation that is obvious is not shocking and one that doesn’t fit the evidence or leaves too many loose ends isn’t fair to readers. So we already have two important criteria: fairness and astonishment (or at least an element of the unexpected).
Another genre that has revelations as essential is romantic comedy. These depend on a secret (usually a lie) by one of the two lovers. It has its own consequences, but it also keeps the lovers from coming together fully.
Notice that the romantic comedy revelation, which usually comes near the end of the story, is different in some ways from the mystery revelation. Readers/audience members not only know it early on in the story, they MUST know it early on. This creates irony and tension. It makes bizarre behaviors credible.
Tootsie provides a great example. The lie Michael (as Dorothy) is living – pretending to be woman makes him unavailable to his heterosexual target of affection for Julie. And, to protect his identity, it puts him into bed with Sandy (a betrayal) and into the arms of Julie’s dad. It’s a lot of fun, and the revelation sets off fireworks, but notice two other important criteria: the point of view (who the revelation shocks) must be interesting and the secret revealed must be consequential, even life changing, to the protagonist. In Tootsie, Julie is shocked and so are Michael’s coworkers. This ties to the consequences, where love and livelihood are both threatened by the revelation.
Notice that revelations, especially shocking ones, are key ingredients of major plot points. Smaller reveals can be part of smaller turns, and, to an extent, each bit of evidence gathered in a mystery is a revelation.
Revelations, of course, are not restricted to mysteries and romantic comedies. Think of how science fiction and fantasy stories disclose facts and relevant details about their worlds to create a sense of wonder. And even a drama like Death of a Salesman, which is grounded in the real world (sometimes this is called straight or mimetic fiction), builds emotion by gradually revealing family secrets and the pain it has engendered in the characters.
It is fair to ask why secrets are kept from readers. A police report or a medical diagnosis or a news story (inverted pyramid) or even a recipe puts the facts out there right away. In reporting, failing to do so is a sin called “burying the lead.” But none of these genres is intended to create emotion (though they may). Fiction always seeks to engage the hearts as well as the minds of the readers. And, while withholding facts may be a disaster in a police report, readers of fiction expect us to withhold or hide facts. There is an agreement between writers and readers. I will tell you lies that deliver truths and you will suspend disbelief willingly.
Truth – it’s the ultimate revelation.