Imagine for a moment that a fundamental assumption you hold regarding your life is false. It’s a lie. You aren’t who you thought you were; someone close to you isn’t who you thought they were; a major incident or force in your life is something other than what you believed it to be. Write about this–what it would be, how you would find out, how you would react, how the secret was kept from you so successfully, and how the discovery would alter your life.
You can also apply this same exercise to a fictional character.