Most good stories start with a fundamental list of ingredients: the initial situation, conflict, complication, climax, suspense, denouement, and conclusion. Great writers sometimes shake up the recipe and add some spice.
Exposition (Initial Situation)
The story opens with a look at Moses Herzog (our titular—tee hee—main man), who is hanging out at a house in the Berkshires and writing a bunch of letters, mostly of which are composed in his head. He's addressing these letters to all kinds of people, from old relatives to dead famous folks.
The letters cover a whole bunch of subjects, but one common thing among them is the way Herzog always expresses his sadness at letting people down or being a general failure in life. He's having a pity party, and no one else is invited.
As we read on, we learn that he's in the Berkshires because he is hiding from the world after a messy divorce. His wife Madeleine left him for his best friend Val. Or maybe "left" isn't the right word. It's more like she tossed him out of his home and his best buddy moved in to replace him. Yowch.
Rising Action (Conflict, Complication)
On the rebound, Herzog has a date with a woman named Ramona, who seems perfect for him. The problem is that Herzog fears he'll be trapped into another marriage if he keeps seeing her… and he's feeling pretty dang anti-marriage after the whole being-tossed-to-the-curb thing. So he runs away to Long Island for a day before deciding to rush back to New York and see Ramona again.
It's clear that he's running pretty hot and cold about how this relationship should play out. He visits his lawyer Simkin and chats about the possibility of ruining his ex-wife in their divorce trial by revealing her affair with his best friend Val. Eventually he visits his very old stepmother in Chicago and steals a gun that his father used to own. It looks like he plans on going to his old home to kill Madeleine and her lover. Yeah, he's acting like an unhinged character in a retro Tom Jones song.
Climax (Crisis, Turning Point)
When he sees his ex-friend Val giving his (Herzog's) daughter June a bath, Moses feels his heart melt. He decides that he's not going kill Val and Madeleine, and let them be happy. Good call, Herz.
The next day, he takes his daughter June out for a day trip. But he gets into a car accident and the police find his concealed gun afterwards. He gets charged with a carrying a concealed weapon, so he needs to call his brother Willie to come bail him out of jail. Ooopsy-daisy.
Falling Action
Once Herzog is out of jail, Willie takes him to see a doctor. Herzog finds out he has a broken rib. Willie doesn't like how his brother is looking (probably a little wild-eyed) and wants him to check into an institution.
Herzog decides instead to retreat to his old house in the Berkshires—the same place that we started this book. During his week of R&R, Herzog keeps composing fake letters to all kinds of people, but as he feels better and better about his life, he writes these letters less often. Phew.
He hears that his would-be lover Ramona is in the area and invites her to come have dinner with him. His brother Willie advises him not to rush into a third (bad) marriage, and Herzog assures him he won't.
Resolution (Denouement)
Herzog bids an aww-inducing goodbye to his brother Willie and gets to work tidying up his house for his dinner with Ramona. A housekeeper comes to help him, and he anxiously wants to tell her how to clean everything properly. But in a peaceful moment, he realizes he has nothing to say to her. His anxiety is gone and he's willing to let things play out however they will.
And that, folks, is probably the best-case scenario for a novel about an unhinged dude thinking about murdering his wife and her lover.