About secrets in general, I always found enlightning this passage from Storming the Wizard's Tower:
Mystery
When an adventure includes a mystery, it’s not always obvious how to run it. You need to give them all the cool information you’ve created, but you also want to preserve the mystery and create suspense. Here’s how, some things to do and things to don’t.
Don’t lead them to the monster, clue to clue to clue. Don’t prepare a trail of leads, or “this person tells you to talk to this person who tells you to go to this place at midnight,” or whatever. Don’t prepare a big reveal. When you run a mystery this way, first of all, you’re the one solving it, not them. Also, you’re setting yourself up for failure – what happens when they don’t follow your carefully prepared trail? Or when they see through it, and treat it as the manipulation it is? What if they predict your big reveal instead of letting you deliver it?
Don’t! It’s a bad way to play this game. Instead, go now and read the four foundational rolls in the chapter about dice. Whenever you feel like you haven’t planned enough, read them again. If you just play those rolls straight, especially the perception and arcane rolls to notice and discover things, and the perception and command rolls for interacting with people, they’ll give the players the information they need, seamlessly and under their control. That’s precisely what those rules are designed to do: let the players, not you, solve the mysteries you create.
Obviously, in this case, substitute "foundational rolls" with "DW moves".