To continue with architecture, Act Two is where things heat up. It is the meat of the story and it should take up about half of your length. This act is typically split into two parts and that creates a nice four part structure. (Why they don't just call it four acts is beyond me. Probably Shakespere is to blame.) Don't confuse acts with parts, it's easy to do, especially if I interchange them. The second part takes place when the hero has become a wanderer. He or she is gathering information and trying to find out just what the antagonistic force is all about. Vogler would call this the Tests and Trials portion of the journey where Allies and a Mentor figure are met. In westerns you have to have a campfire scene here. In romances you probably have the boy loses girl part here.
There is one specific scene that needs to happen in this part. Brooks calls this Pinch #1. You have to pinch your readers to remind them what the danger is and what's at stake. This is best done in a very blatant way, most likely after a particular test or trial is failed. You could also have one of you allies show up and save the hero. For Vogler this would be the Approach to the Inmost Cave. Beware, here there be monsters.
At the midway point of Act Two, which is also the mid point of the novel, you have a major revelation of information that completely changes the course of the story. Before that, your wandering hero was searching for clues. After it, your hero has the info he or she needs and is ready to become a warrior. They have stopped reacting to events and they start being proactive. Now they take the fight to the antagonistic force. Vogler places this as the Supreme Ordeal. In Star Wars this is the time spent on the Death Star and the midpoint is the revelation that R2 has the plans necessary to destroy it. From that point on, we're no longer just flying to Alderaan, we're trying to save the galaxy.
The proactive time after the midpoint also should include Pinch #2. Once again the hero and the reader need to be reminded in a pointed way that there is a real possibility of failure. The antagonistic force shows up again but this time we have new knowledge and the stakes have been raised. The antagonist is now more dangerous than ever before.
All this leads to Plot Point #2 and the end of Act Two. Act Three is the resolution and I'll discuss that later.