James Thurber often wrote humor pieces about the friction that exists between men and women, and especially between husbands and wives. One of the best of these stories is "A Couple of Hamburgers." "The Unicorn in the Garden" has no particular moral as such. Thurber is just illustrating the fact that friction does exist between husbands and wives in many marriages. He did a whole series of cartoons titled "The War Between Men and Women," which was reprinted in his anthology titledThe Thurber Carnival. There are many other cartoons in that book showing husbands and wives in conflict. His male characters are typically impractical dreamers like the husband in "The Unicorn in the Garden" and like the hero of "The Secret Life of Walter Mitty." His female characters are often hard-core realists and intensely practical. Thurber is probably best remembered for his stories and cartoons dealing with domestic infelicity.
The wife in the story was sure that her husband was insane and he was to be institutionalized. She went ahead to call the police and the psychiatrist to assess the situation. She gloatingly gave her account of the events to the officials. However, the man did not corroborate her statement and instead the woman was considered crazy and institutionalized. This brings us to the moral of the story which is "don’t count your chickens before they are hatched".
The Unicorn in the Garden tells a story of a man who sees a unicorn in his garden but on asking his wife to come witness the spectacle, she dismisses him as crazy. The wife tells the husband that he should be institutionalized and the man eventually leaves dejected. The woman is sure that the husband will end up in an institution and even makes arrangements towards this eventuality, but she ends up being institutionalized herself.