This short story by Nathaniel Hawthorne focuses on five old friends: Dr. Heidegger, the host, and four other elderly people he invites to his house for the purpose of conducting an experiment. These guests are Mr. Medbourne, Colonel Killigrew, Mr. Gascoigne, and the Widow Wycherly. In their younger years, the three male guests competed for Widow Wycherly’s hand. Now, all are extremely old and withered. Dr. Heidegger asks his old friends if they will take part in an experiment. This is not uncommon for the doctor—he is prone to engaging his friends in experiments on a small scale. Thus far, they have only witnessed events such as examining a cobweb under a microscope. 

This time around, he shows them a dried rose, as "ancient" as if it were about to turn into dust. The rose was given to him by his fiancée, Sylvia Ward, to wear on their wedding night some fifty-five years ago. There is a portrait of Sylvia in the doctor’s study, and it is said that Sylvia took a prescription pill on her bridal night and died. He asks his friends if they think the dried, decades-old rose will ever bloom again. Of course, the friends say this is impossible, but Heidegger takes out a vase of water and throws the rose into it. Immediately, the rose begins to bloom again. Heidegger explains that this is no trick—he has found the Fountain of Youth in southern Florida. 

The old friends are still skeptical. The Colonel asks what effect the water may have on humans, and the doctor says he may judge for himself. Filling four champagne glasses, he offers them to his friends, saying that he himself does not wish to participate in the experiment. He has gone to great lengths to grow old, he says, and does not wish to return to youth. He warns his companions that they ought to be “patterns of virtue and wisdom” in their new youth since they have a lifetime of experience.

The friends' skepticism disappears as they take a drink. Immediately, they appear slightly less aged. Rosiness returns to their “corpse-like” features. They clamor for more, and Heidegger begs them to have patience, saying that as they have grown old so slowly, they should be content to grow young again over the course of half an hour. However, he offers them another glass, and another, and the guests all delight in the slow return of their youth.

Eventually, they are properly young again, filled with vigor. The male guests are impassioned by their love for the widow, being young once again, and in their rush to dance with her, they knock over the vase, spilling the water upon the floor. As the friends cavort, a mirror in the study seems to show that they are not really young, but still elderly figures behaving like youths.

Dr. Heidegger says he must "protest against this riot" in response to the upset. The guests all stand still, and, turning to Dr. Heidegger, see that the rose is beginning to wither again. The same begins to happen to the elderly people, who realize that the Water of Youth has only a transient effect. Dr. Heidegger says he does not "bemoan" this, for he has no desire to be young again if it is only temporary.

The friends disagree, however—they decide to go to Florida, find the Fountain of Youth, and drink from it constantly so that they will stay young forever.