Creating a pivot point

My enjoyment of exposition may destroy me. However, handling moments of explanation correctly will probably stave off the inevitable execution of my writing life. This latest chapter I'm looking at is a minefield in terms of how much to relate, and the manner in which it is related. It's good that I have reasons for things - actions, events, happenings - but such explanations can have a soporific slowdown effect that can kill any story if not enough control is employed. I'm aware of it, so believe I can take care of it. This particular chapter needs handling with that kind of care and what is mighty important is the bit I leave out. Too much information and the narrative will falter; too little information and the reader may create his own version. A dangerous situation: for who is the writer? We may well ask.  This particular chapter provides an opportunity to explain something important. It must not become an explanation as to why the story fails at this point. Words better not fail me...