Mr. Vogler calls what I consider the dreaded "Black Moment" as the upreme ordeal. I once wrote a piece called Is Your Black Moment Really Gray. I'm sure some bits and pieces of it are still floating around the internet and there is an expanded version in the book Jane and I wrote.
This is the moment when the focus character reaches rock bottom. The hero has lost the heroine. The murderer will escape. The prince or princess will never emerge from the dungeon. The build up to this scene should flow with tension like hovering at the edge of the cliff waiting to take the plunge. This is adrenalin time.
Mr. Vogler says the hero or heroine in this part of the story meets his or her greatest fear. The reader needs to fear and wonder if the character will suffer defeat or will triumph. Every story needs such an event. My own take is that this should be played out to the nth degree.