Story about a paranoid patient in a mental hospital, who believes that his wife is conspiring with his doctor

Question

A man is in a mental hospital as a patient. He is suspicious of everything around him and believes that his wife is conspiring with his doctor. He also plays chess with his doctor.

Answer 1

"They", not a novel but a short story by Robert A. Heinlein, which was also the answer to the old question Short story where rain only on one side of the house gives away fake world?; first published in Unknown Fantasy Fiction, April 1941, available at the Internet Archive. You may have read it in one of these compilations.

ISFDB synopsis:

A patient in a psychiatric hospital believes everyone is an actor or a robot devoted to making him believe in "reality", and only in his dreams can he see through the delusion.

Wikipedia plot summary:

The story concerns an unnamed man who is confined to a mental institution because he is suffering from the delusion that he is one of the few "real" entities in the universe, and that the other "real" entities have created the rest of the universe in a conspiracy to deceive him. He spends much of the story engaged in verbal sparring with the psychiatrist who is caring for him, and in pondering his predicament, trying to figure out a way to prove that his belief is true. On the final page of the story, the reader discovers that his belief is true; the god-like character "the Glaroon" is behind the conspiracy. However, this revelation is kept from the protagonist.

He also believes that his wife is conspiring with his doctor. He does play chess against his doctor.

He got out the chessmen and commenced setting them up. "What do you know of my case so far?"

"Very little. Physical examination negative. Past history, negative. High intelligence, as shown by your record in school and your success in your profession. Occasional fits of moodiness, but nothing exceptional. The only positive information was the incident that caused you to come here for treatment."

"To be brought here, you mean. Why should it cause comment?"

"Well, good gradious, man—if you barricade yourself in your room and insist that your wife is plotting against you, don't you expect people to notice?"

"But she was plotting against me—and so are you. White, or black?"

"Black—it's your turn to attack. Why do you think we are 'plotting against you'?"

"It's an involved story, and goes way back into my early childhood. There was an immediate incident, however—" He opened by advancing his white king's knight to KB3. Hayward's eyebrows raised.

Of course, this being a science fiction story, the patient's "paranoid delusions" are correct:

The creature he knew as Alice went to the place of assembly without stopping to change form. "It is necessary to adjourn this sequence. I am no longer able to influence his decisions."

They had expected it, nevertheless they stirred with dismay.

The Glaroon addressed the First for Manipulation. "Prepare to graft the selected memory track at once."

Then, turning to the First for Operations, the Glaroon said: "The extrapolation shows that he will tend to escape within two of his days. This sequence degenerated primarily through your failure to extend the rainfall all around him. Be advised."

"It would be simpler if we understood his motives."

"In my capacity as Dr. Hayward, I have often thought so," commented the Glaroon acidly, "but if we understood his motives, we would be part of him. Bear in mind the Treaty! He almost remembered."

The creature known as Alice spoke up. "Could he not have the Taj Mahal next sequence? For some reason he values it."

"You are being assimilated!"

"Perhaps. I am not in fear. Will he receive it?"

"It will be considered."

The Glaroon continued with orders. "Leave structures standing until adjournment. New York City and Harvard University are now dismantled. Divert him from those sectors.

"Move!"