Patrick spoke to Mary for about five minutes, obviously explaining why he wanted a divorce. His reasons, however, are not spelled out in the text. We have to guess why he has made such a radical decision as to move out and file for a divorce. There is another good short story which actually comes close to spelling out what is wrong with the Maloney marriage. That story is "The Chaser" by John Collier, a writer who had many similarities to Roald Dahl, including a quirky sense of humor. Here is what the old man tells his young customer Alan Austen who is head-over-heels in love with a girl named Diana and wants to buy a potion that will make her feel the same way:
"She will want to know all you do," said the old man. "All that has happened to you during the day. Every word of it. She will want to know what you are thinking about, why you smile suddenly, why you are looking sad."
"That is love!" cried Alan.
"Yes," said the old man. "How carefully she will look after you! She will never allow you to be tired, to sit in a draught, to neglect your food. If you are an hour late, she will be terrified. She will think you are killed, or that some siren has caught you."
The old man is preparing Alan to be a future customer for his "chaser," an undetectable poison which can rid a man of a spouse who is suffocating him with her attention. The women the old man is describing sounds very much like Mary Maloney, and we can assume that she is having the same effect on Patrick that other wives have had on the men who came to the old man for the "chaser."
Another story in which a man is being tormented by an overly attentive wife is "The Secret Life of Walter Mitty." The protagonist does not think of resorting to divorce or murder, but he escapes from his wife into a secret fantasy world where she cannot follow him because she doesn't know of its existence. When he is sitting in the hotel lobby fantasizing about being a World War I ace pilot, she bursts into his illusions with the following acrimony:
“I’ve been looking all over this hotel for you,” said Mrs. Mitty. “Why do you have to hide in this old chair? How did you expect me to find you?”
"Hiding" is exactly what Mitty was doing. And he was probably hoping she wouldn't find him.