First off the marriage is a wreck from the get go. So they decide to go on a hunt in Africa to see if they can rekindle there lost romance. Its just Macomber his Wife Margot and their guide Wilson. during the hunt with Wilson macomber runs away from a loin they had shot when it jumped at the two when they tired to finish it off. Is wife hates this and runs away crying from the dinner table. later on in the story Margot sleeps with Wilson because Wilson is more of a man than her husband and she is turned on by that. The story ends when they are hunting buffalo and this time when they go in for the kill macomber doesn't run away but stands his ground and his wife shoots from the car and kills him.
What i think about this story is Margot didn't want a husband that wasn't going to be a man that's why she slept with Wilson. When macomber finally got a hold of this idea and he started to change the way he acts to stand up for himself, she didn't like that. Margot had gotten used to the idea of a weak husband and didn't want to give up that power. So i believe she killed her own husband.