Dr. Heidegger, an elderly medical doctor who is the subject of many fantastical rumors, invites four friends into his study to conduct an experiment on them. The friends, Mr. Medbourne, Colonel Killigrew, Mr. Gascoigne, and Widow Wycherly, are all elderly people whose reputations have been tarnished in one way or another. The three men, moreover, were once bitter rivals, competing for the affection of Widow Wycherly, who was very beautiful as a young woman (but is now, like all her friends, quite decrepit). All (including Dr. Heidegger) are regarded by others to have gone a bit out of their minds, having suffered greatly in their lives.
Dr. Heidegger’s study, where the friends are gathered, is a dusty place full of countless curiosities, among which are a human skeleton, a portrait of Dr. Heidegger’s long-dead fiancée, a bust of Hippocrates, an enchanted mirror that is rumored to contain the souls of all Dr. Heidegger’s dead patients, and a mysterious magic book. Dr. Heidegger removes the book, and takes a pressed rose from its pages, explaining that his fiancée, Sylvia Ward, gave it to him fifty years before, and he had intended to wear it at their wedding, but Sylvia had died on the eve of their wedding. Dr. Heidegger places the rose in a vase at the center of the table around which they’re gathered, and slowly it comes back to life, until it looks as though it has just bloomed. His friends think it is a deception, but Dr. Heidegger explains that the water in the vase is from the fabled Fountain of Youth which was sought after by Ponce de Leon for so long. He then invites his skeptical friends to drink as much of the liquid as they please, and pours a champagne glass for each of them. Dr. Heidegger explains that he won’t be drinking any of the liquid—only observing.
Before the four friends drink their glasses, Dr. Heidegger advises them that perhaps they should draw up a few general rules for themselves, since they are about to journey for a second time through “the perils of youth,” and perhaps they could benefit from the wisdom of old age. But the friends laugh at Dr. Heidegger’s warning and gulp down the water. Almost immediately, they begin to feel somehow revitalized, their spirits lifted. The water restores life and color to their aged bodies, and seems to smooth away some of their wrinkles. Skepticism quickly vanishing, they ask for more, and Dr. Heidegger obliges, filling their glasses.
With the second glass, the group has reached middle age again, and they seem somewhat drunk. Colonel Killigrew remarks that Widow Wycherly is an attractive woman again; she runs to the mirror to check. Mr. Gascoigne begins talking politics, though it’s unclear exactly what he’s saying or what year he thinks it is. Colonel Killigrew busies himself by singing a drinking song and ogling Widow Wycherly. Mr. Medbourne sets about hatching a half-baked, far-fetched business scheme. Intoxicated by the water’s effect, the group asks for another glass to be poured.
Now, they are in the prime of their youth, and they mock Dr. Heidegger’s sickly and decrepit appearance, as well as their own old-fashioned clothes, as if they have forgotten that they themselves were, moments prior, also old and infirm. The Widow invites Dr. Heidegger to dance with her, but he explains he’s too old. The other three men argue over who will be her dance partner, each of them placing a hand on her and struggling amongst themselves. The narrator remarks that it is said that the mirror on the wall reflected three sickly old men fighting over the body of a withered old woman, rather than the four of them in their youthful prime. In their fighting, they knock over the table, spilling the vase full of water. The water touches a butterfly on the verge of death, which springs back to life and lands on the white-haired head of Dr. Heidegger.
Dr. Heidegger calls for an end to the chaotic fighting, and it is as if Father Time himself were “calling them back from their sunny youth;” the four friends retake their places around the table. Dr. Heidegger exclaims that his rose has wilted again, but reflects that he loves it just as much as when it was freshly-blossomed. In the next instant, the four friends notice that they, too, seem to be aging again with every moment that passes. Soon, they are back to normal, and the Widow remarks that if she can’t be beautiful, she’d rather be dead. Dr. Heidegger remarks that watching his friends’ behavior has confirmed for him that he would never drink from the Fountain of Youth, even if it gushed at his at doorstep and its effects lasted for years. His friends, however, feel otherwise: they decide to travel to Florida, where the Fountain of Youth is, and drink from it morning, day, and night.