You can find an overview here.
I mentioned in the post describing the first half of Act Two that the Midpoint is a critical component in your structure. It is a demarcation between the first half of the Second Act, where your hero is in “reaction” mode, and the second half of Act Two, where your hero transitions to Warrior/Attack mode.
Information gained at the Midpoint pulls the curtain back on what’s actually happening, And because your MC now knows what’s actually happening, they have a target to focus on, instead of random, reactive activities. In the first half of Act Two, the MC is floundering in their attempts. After the midpoint, they are more focussed and targetted. They don’t have all the information yet, but they have enough to head in the right direction.
In this part of your story, make sure you make the transition to attack. The attack needs to continue until the Second Plot Point, at which point the MC finds the final pice of the puzzle and crashes into Act Three hell-bent for the finish line. More on Act Three next week(ish)
Halfway between the Midpoint and the Second Plot Point, toss your readers a Pinch Point. And since it’s the second Pinch Point, it should be a scene that demonstrates the lengths to which the MC will go to get to the finish line.
And just before Act Two ends, just before the final piece of the puzzle points him to his solution, make the MC’s life miserable. Make it look like everything has been for naught and that they have failed. Then, and only then, the final pice of the puzzle that makes up the Second Plot Point.
Next up, Act Three. The Resolution and all that it entails.