Secrets are one of the best ways to introduce a driving force into the plotline of a book, because people are naturally curious. We want to know. We want to understand. There are entire genres of books and TV shows and podcasts and movies built around solving mysteries, unraveling historical puzzles, uncovering family secrets. Investigative journalism is about uncovering the truths that powerful entities seek to hide.
A secret in a book is like the gun that must go off. Whether or not all the characters in the book learn the secret, the reader must find out the answer. (There’s an exception for nonfiction in which nobody knows the answer—but the author has to offer something, some reason for the reader to tolerate the dissatisfaction of an unanswered question.)
Although my first book was called The Secret Year, the reader was in on the main character’s secrets from the beginning (however, the secondary characters had some surprises for him along the way). The tension was around how long he could keep his secret, and what would happen if it came out.
But in my second novel, Try Not to Breathe, a character’s secret played a huge role in the climax of the book. I wrote the first draft not even realizing that a major character was keeping a secret from the main character—and even from me, the author! When I realized this person hadn’t told the truth about a pivotal event, it opened up the path to the final conflict, and it explained a lot about this character’s motivations. Everything fell into place so smoothly that it was clear that one part of my brain had been keeping a secret from the other.
Which was fine with me, as long as that part revealed its plan in time to make it into the book. It’s one of the delights of writing: the things we discover as we write, the things we’ve known without knowing.