Then I remembered the earlier incident I had put in, where the hero had spotted a nasty piece of blood magic. Which I left dangling.
There's only so much you can justify leaving out because the point-of-view character is being left in the dark (for his own protection) by the other characters. Especially when, right before the climax, I throw in two characters who know a lot about what's going on and have learned there is good reason to let them (the POV character and some younger ones) in on the secrets, despite their youth and the danger they will eagerly plunge into situations that could kill them.
Unless, of course, I go back and excise that incident. And replace it with something that will serve exactly the same narrative function while leaving nothing danging. . . .