For a three-act plot analysis, put on your screenwriter’s hat. Moviemakers know the formula well: at the end of Act One, the main character is drawn in completely to a conflict. During Act Two, she is farthest away from her goals. At the end of Act Three, the story is resolved.
Act I
Moses Herzog sounds like he needs to go into a mental institution. He sits around on his own all day and writes fake letters to the president and dead relatives.
But can you blame the guy? His wife did just dump him for his best friend Val. Plus she kicked him out of his own house and took out a restraining order against him. To make matters worse, Herzog's career is in shambles, and he has lost track of why he bothers getting up in the morning. But then out of the blue, a beautiful woman named Ramona falls head over heels in love with him and wants to date him. Herzog is worried about rushing into another relationship, so he keeps his distance.
Act II
Herzog visits his lawyer Simkin to find out whether there's anything he can do to make life hard for Madeleine and Val. He wants to take an already messy divorce and make it filthy-messy, and he has some ideas about how he can go about this. He could sue for custody of his child, June. He could make a good case against Madeline if he brings up the fact that she and Val had an affair while Madeleine and Herzog were still married.
The trial would humiliate Herzog, but he wants to go ahead with it out of sheer spite if it means hurting Madeleine and Val, too. Eventually, Herzog travels to Chicago to pay Madeleine a visit, despite the restraining order against him. He stops by his old stepmother's house first to grab his father's old pistol, which has two bullets in it. Oooh: a man out for revenge with a gun. What could possible go wrong?
Act III
As it turns out, not much goes wrong at all. Herzog goes to Madeleine's house with a vague plan of murdering her and Val. But when he sees Val tenderly giving his (Herzog's) daughter June a bath, Herzog can't go through with his dumb plan. He leaves and arranges to spend the next day with June. But they get into a car accident and the police find the loaded pistol that was in Herzog's pocket.
Herzog gets booked for a gun violation and needs his brother Willie to bail him out. Willie wants Herzog to check into a mental institution (huh—wonder why?) but Herzog goes to his secluded house in the Berkshires instead. The week of R&R seems to restore his mental health. He ends the book preparing for a visit from his new lover Ramona.