The story opens with Horacio searching the bridges of Paris for his lover, a Uruguayan woman named Lucia (better known throughout the novel as la Maga), who has disappeared.

This is a circle of artists, writers, and musicians that drink and listen to music while discussing art, literature, philosophy, architecture, and other subjects.

In their discussions, they frequently mention a writer by the name of Morelli, who insists on the necessity of breaking with the linguistic forms of the moment.

The group jumps from one topic to another with relative ease, but la Maga, who is not as well-read as the others, generally needs the others to explain the subjects at hand.

Rocamadour's health is too delicate to improve in the cold and cramped apartment, but la Maga is terrified by the idea of sending him to a hospital.

To take cover from the poor weather, he steps into the entrance of a theater and decides to stay and watch the piano concert being given there by a madame Berthe Trepat.

After reflecting on the senselessness of the death and considering the confusion that the event would cause, Oliveira, with his habitual attitude, decides not to communicate the terrible news.

The group embarks on one of their characteristic philosophical discussions, during which they discreetly communicate to each other about the horrible event that had come to pass in the apartment.

Gregorovius, who is now living in the apartment, implies that la Maga may have returned to her native Montevideo, but Horacio doubts that she has the means to afford the trip.

It opens with a brief introduction to the life of Manolo Traveler, Horacio Oliveira's friend from childhood, who lives in Buenos Aires with his wife Talita.

Horacio then settles with Gekrepten in a hotel room located directly across the street from the flat Traveler and Talita share, where his mind slowly begins to unravel.

Horacio, meanwhile, observing the relationship between Traveler and Talita, who more and more reminds him of La Maga, endeavors to enter more intimately into their lives, but he is unable to do so.

On the day the ownership of the hospital is to be transferred, they are told that all the inmates must agree to the deal by signing a document, and that the three of them must act as witnesses.

The place is dark and eerie in the long hours before dawn, with the three often seeking refuge in alcohol and conversation in the pharmacy's warmer atmosphere.

One night Horacio is smoking in his room when he sees Talita crossing the moonlit garden below, apparently heading to bed.

A moment later, he thinks he sees La Maga appear and begin a game of hopscotch in the same general area; but when she looks up at him, he realizes it is Talita, who had turned and recrossed the garden.

A kind of guilt, fed in part by the institution's gloomy atmosphere, begins to steal into his musings, and it is not long before he conceives of the idea of someone's trying to murder him while he is on duty—perhaps Traveler.

The hours pass slowly and painfully, but finally Traveler does try to come in, and the tumult that results brings Dr. Ovejero and the others out into the garden, where they find Oliveira leaning out the window of his room as if intending to let himself fall.

Only by proceeding to read the "Expendable Chapters" will the reader be able to place Horacio firmly back inside the mental institution, where, after being sedated by Ovejero, he succumbs to a lengthy delirium.

The third section of the book, under the heading "From Diverse Sides", does not need to be read in order to understand the plot, but it does contain solutions to certain puzzles that arise during the perusal of the first two parts.

Most of these notebooks are unpublished and Oliveira not only considers doing this work as a great honor to himself personally, but also as perhaps the best chance yet of his attaining the ninth square in his lifelong game of spiritual, emotional, and metaphysical hopscotch.

Oliveira's lover in Paris, she is lively, an active participant in her own adventures, and a stark contrast to Horacio's other friends, with whom he has formed a philosophical social circle called the Serpent Club.

Talita bears a striking similarity to Horacio's great love interest, La Maga, while Traveler is referred to as his "doppelgänger."

The relationship that develops between the three centers around Oliveira's interest in Talita, which seems disingenuous, and Traveler's attempts to lessen Horacio's metaphysical burden.

Minor characters of note include Madame Berthe Trepat, a composer who mistakes Horacio's attention for sexual interest, and a homeless woman named Emmanuele with whom Oliveira has a brief, disastrous tryst shortly after La Maga's disappearance.

Horacio says of himself, "I imposed the false order that hides the chaos, pretending that I was dedicated to a profound existence while all the time it was the one that barely dipped its toe into the terrible waters" (end of chapter 21).

Order versus chaos also exists in the structure of the novel, as in Morelli's statement, "You can read my book any way you want to” (556).

Talita argues a similar point in her seesaw-questions game with Horacio, who believes that only when one lives in the abstract and lets go of biological history can one achieve consciousness.

For Horacio, life is a series of artistic flashes by which he perceives the world in profound ways but still remains unable to create anything of value.

The novel was the inspiration for Yuval Sharon's 2015 production of Hopscotch, an opera by six composers and six librettists set on multiple stages in Los Angeles.