The Button baby is born in hospital in 1860, at a time when most children were traditionally born at home. The reaction of the doctor who delivered the baby, Dr. Keene, and the nurses at the hospital is rude and cruel. Dr. Keene is concerned that his “professional reputation” will be damaged by the delivery of such a child, and the nurse reacts with “utter terror.” This all happens before the peculiarity of the child is revealed. Benjamin, as he is later named, is “a baby of threescore and ten” complete with a long white beard. Mr. Robert Button is shocked when he is told he has to take the baby home: he is mortified at the idea of being seen with “this appalling apparition.” He is concerned about what people will think when they see the strange child, and he struggles to imagine how he will explain the situation.
Robert Button goes out to buy clothes for the child, who he considers calling Methuselah, after the longest lived man in the Bible. Mr. Button ends up finding only a costume suit, and when the child complains, Mr. Button is savage, telling his son, “You’ve made a monkey out of me!” The boy gives in to this rudeness with “a grotesque simulation of filial respect.”
Mr. Button sees Benjamin as “a poor excuse for a first family baby.” He does not react as Mr. Button wishes, rejecting warm milk and “obediently” but joylessly shaking his rattle. Benjamin starts to sneak his father’s Havana cigars and to read the Encyclopedia Britannica. People say the boy looks like his grandfather, which does not please the family. They organize play-dates with other children, which he does not enjoy. However, when he broke a window with a slingshot he “secretly delighted his father.” Benjamin then strives to break something every day to be “obliging.” Benjamin is more at ease with his grandfather. He is sent to kindergarten aged five, but keeps falling asleep and so is removed. When he is twelve, Benjamin asks to be allowed to wear long trousers. His father agrees, though he tells his son “Fourteen is the age for putting on long trousers.” This is part of Mr. Button’s “silent agreement with himself to believe in his son’s normality.”
Benjamin enrolls at Yale, but, unable to find his hair dye on the third day, he is thrown out as “a dangerous lunatic.” He decides he will go to Harvard instead.
In 1880 Benjamin is twenty, and he and his father look like brothers. They go to a dance and Benjamin meets Hildegarde Moncrief who is “as beautiful as sin.” He reacts physically to her presence - “an almost chemical change seemed to dissolve and recompose the very elements of his body.” Hildegarde is attracted to him as she thinks he is fifty and therefore would make a sensible and reliable companion.
Benjamin and Hildegarde are engaged six months later. General Moncrief is devastated and speculation begins anew as to Benjamin’s origin. He is variously thought to be a former prisoner, his own grandfather, an assassin or a devil. No-one is really interested in the truth. General Moncrief tries to put his daughter off the marriage, but Hildegarde has chosen to marry for mellowness.
The Button family fortune doubles. General Moncrief begins to appreciate his son-in-law as he arranges publication of his twenty-volume history of the Civil War. He makes a fantastic business decision about nails, which saves the company money. Benjamin looks younger every year and he loses interest in Hildegarde. He joins the army to fight in the Spanish-American War of 1898.
On his return from the war, Benjamin is depressed to see how gray Hildegarde has become. He realizes that he will keep getting younger when he had hoped the strange process would stop. Hildegarde blames Benjamin for his changes, saying he is “stubborn.” Meanwhile, Benjamin gets younger and stronger. He takes up golf and is an excellent dancer. His son, Roscoe, graduates from Harvard.
Ten years after his son graduates, Benjamin goes to Harvard again. He plays football against Yale and scores seven touchdowns and fourteen field goals, and is greatly celebrated as a remarkable freshman athlete. But as his college career continues, Benjamin ages into the physique of a typical teenager, and he does not even make the team in his senior year. Hildegarde moves to Italy, so Benjamin moves in with his son. He asks to go to St Midas’ prep school. Roscoe says he is too busy to help, telling Benjamin his “joke” has gone too far. He tells Benjamin that he must call him uncle.
Benjamin at fifty-seven enjoys reading Boy Scout stories. He receives a letter explaining that former officers from the Spanish-American War are being called back in to service. He has a new general’s uniform made and turns up at Camp Mosby, but he is considered a playful child. Roscoe arrives to take him away in disgrace.
Roscoe’s son is born in 1920. Roscoe condemns his father for not behaving like “a red-blooded he-man.” Benjamin and his grandson go to kindergarten on the same day. As his grandson moves through the classes, Benjamin goes backwards until he is removed as he becomes afraid of bigger children.
Benjamin does not recall his earlier, older days. He slides into a milk-scented dark haze and then…nothing.
A notable omission from the story is any reaction from Benjamin’s mother regarding the birth and growth of her son. This suggests that Fitzgerald was not interested in exploring the full implications of this magic-realist scenario, but rather that the intent was to explore the relationships between fathers and sons when their age difference is not constant.
Benjamin’s condition is a trial to everyone, and he is constantly criticized for the effect his unusual state has on others. First the doctor and the nurse condemn his birth as troublesome, embarrassing and damaging to their reputation. There is no compassion for the child or his mother. Roger Button sees his new son as “grotesque," describing him as an “appalling apparition." This lurid language and unfeeling reaction is reminiscent of Dr. Frankenstein's response to his creature.
Mr. Button is concerned only with what others will think of his child, and not about his son's feelings. Even more remarkably, no one in the story attempts to discover the reason for Benjamin's condition, nor to cure it through any means except absurd socialization efforts. It is this aspect that makes the story more an example of magic realism than of fantasy: the narrative's acceptance of the outlandish phenomenon within an otherwise recognizable world is a key characteristic of the magic realism genre.
When Benjamin is thrown out of Yale, he begins to see that it is easier to be as others see him rather than as he really is. Hildegarde Moncrief believes Benjamin is fifty, and they live this lie as a couple until she moves to Italy when he begins prep school. She behaves as if his condition were a choice: that he is “stubborn” and is acting this way out of a lack of consideration for others.
As he moves into his older, more juvenile years, Benjamin loses the memories of the past. His story ends in darkness, as his life presumably ends with his birth. This arc is structurally echoed in Flowers for Algernon, in which Charlie begins the story in an intellectual darkness, grows into mental genius, and then declines back into darkness. Both stories use a fantastic or science fictional premise to explore the structure of all long lives, in which we are cognizant of being on a long, slow decline back into the oblivion from which we came.