A middle-aged husband and wife are on permanent bad terms and would like to be free of each other. The man comes into the house and tells his wife he has seen a unicorn in the garden. She seizes on this as an opportunity to get her husband committed to an asylum where he will be out of her way and she will have control of their joint assets. She makes a phone call to have her husband taken away to the asylum, but when they get there the husband says there is no such thing as unicorns and that his wife must be having one of her delusions. The men end up taking the wife away to the asylum instead.
This story is similar to Thurber's "The Catbird Seat." Many of Thurber's best stories are to be found in the anthology titled The Thurber Carnival, which also is full of his wonderful cartoons. One of Thurber's favorite themes in his stories and cartoons was what he sometimes called "The war between men and women."