A novel that almost defies summary, Infinite Jest begins with a scene at the latest chronological point in the purview of the novel: in the "Year of Glad," the final year of nine-year-long Subsidized Time calendar in O.N.A.N., a nation made up of parts of the former United States and Canada. The novel opens with a scene of Hal Incandenza, unable to verbally communicate for reasons as yet undetermined, undergoing an admissions interview with faculty and coaching staff at the University of Arizona. The interview devolves into chaos as Hal seems to have a panic attack and is promptly rushed to the hospital.
Hal's personal arc begins when he's a toddler and he swallows a clump of strange mold from his family's basement. His mother, Avril Incandenza, freaks out and parades Hal around their backyard screaming for help from the neighbors. This memory returns as an important moment for Hal and his brother Orin, because at this moment Avril's usually extremely collected and curated facade of self is exposed; both brothers look to this moment as a "true" depiction of the crippling anxiety that simmers just beneath the surface of Avril's public persona.
Their father James O. Incandenza is a physicist and Avril is a grammarian and English professor at Brandeis. James opens the Enfield Tennis Academy when Orin is a preadolescent child still competing in regional tennis. James was introduced to tennis by his own father, who had ambitions of being a great player but destroyed his knees in a match and could never fully recover. James's father was also a commercial actor of small acclaim, and the combination of tennis and film followed James into his own adult life in a major way. When James founds E.T.A., the family moves from Waltham to Boston, which is a hard move for Avril who likes their suburban life. Avril grew up on a Quebecois potato farm, and Charles Tavis is her step-brother (arguably half-brother, but evidence later in the book suggests that C.T. and Avril are in no way blood-related). C.T. takes over the Headmaster position after James ends his own life with a rigged microwave.
At Enfield, James had become increasingly withdrawn. He focused more, in the final years of his life, on making films than on administrating a school. Mario, the middle Incandenza brother, acted as James's assistant and protégé, which he could do because due to a long list of developmental and congenital issues, Mario is unable to play tennis, so his commitments at E.T.A. are significantly less than those of the rest of the students. Orin, Hal's oldest brother, plateaus in his tennis achievement around age fifteen and, instead of trying to go pro or trying to improve on a satellite tour, he matriculates at Boston University on a full scholarship with a stipend for tennis. But before the season even starts, Orin decides he wants to switch to football, because there is this baton twirler to whom he and his friends refer as the PGOAT or Prettiest Girl of All Time. Her name is Joelle van Dyne, a.k.a. Madame Psychosis.
Most of the plot takes place in the Year of the Depend Adult Undergarment (Y.D.A.U.). Time, in Wallace's speculative future, has been subsidized. Time has been subsidized because the third-party candidate and famous Las Vegas-crooner-turned-politician Johnny Gentle has won the presidency on a platform to literally clean America. Gentle is the head of the Clean U.S. Party (a.k.a. C.U.S.P.) and also suffers from O.C.D. and is an extreme germaphobe. Under Johnny Gentle, North American countries have been joined into "Interdependence" in one mega-country called O.N.A.N. or Organization of North American Nations, and Johnny Gentle appoints himself the head of O.N.A.N. Gentle runs on the promise to launch all American trash into space, but after several shuttle malfunctions, Gentle's administration shifts the approach to designating a huge territory to serve as a landfill. Most of New England and the entire border of Quebec is turned into what Americans call "the Great Concavity" (and what Canadians refer to as the Convexity). Massive trebuchets target the Concavity, flinging garbage to its Eastern side and resulting in unprecedented environmental cycles.
Gentle, being so offended by trash and uncleanliness of any sort, is disgusted by the Concavity. As the leader of O.N.A.N., he cedes the territory as a "gift" to Canada. Of course, the Canadian Prime Minister doesn't want the land, but Gentle presses him until he acquiesces. To make matters worse, reconfiguration of state lines has cost the U.S. government a tremendous amount of money. In order to pay for reconfiguration without raising taxes, the Gentle administration proposes Subsidized Time, which allows corporations to pay tremendous amounts of money to sponsor the year; they pay for the right to have the year named for them, for example Burger King wins the bid for Year of the Whopper. Most of the novel takes place in the penultimate year of Subsidized Time, Y.D.A.U., and the first scene of the novel, when Hal has a breakdown in his admissions interview, takes place during the Year of Glad (the next and final year of Subsidized Time).
Even prior to the formation of O.N.A.N., there exists in Canada a major separatist movement in Quebec. Many paramilitary organizations operate with the goal of making Quebec its own country, and the formation of O.N.A.N. and especially the Concavity, which dominates Quebec's southern border and poses a serious environmental threat to the health of the province's inhabitants. A particularly violent Quebecois separatist group, the Assassins Fateuils Roulents (A.F.R)—in English the "Wheelchair Assassins"—figure significantly into the plot.
There are two roughly parallel plotlines happening in Infinite Jest; the first and arguably "primary" plotline takes place at Enfield Tennis Academy, while the secondary one—just as integral to the overall architecture of the novel—takes place down the hill from E.T.A. at Ennet House, a halfway house for recovering addicts. As with E.T.A. around Hal, with Ennet House there is an entire extended cast of characters that revolves around the deuteragonist, Don Gately. Don Gately is an ex-professional burglar who is court-ordered to the halfway house after one of his burglaries goes terribly wrong. Don always tried to avoid violence in his life of crime, but the victim of his final breaking and entering, a man named DuPlessis, happened to have a severe head cold when Don tied him to a chair and gagged his mouth. DuPlessis died of suffocation because he couldn't breathe out of his nose. DuPlessis also happened to be a rabid anti-O.N.A.N. organizer for French-Canadian separatist groups. This is the earliest discernible crossover between the main plotlines and the Quebecois separatist effort.
Throughout the book, Wallace repeatedly cuts back to a conversation taking place between Remy Marathe, an agent of the A.F.R., and Agent Steeply of the U.S. Office of Unspecified Services. Marathe and Steeply represent two opposing sides of the Quebecois separatist conflict, but Marathe is a double (or perhaps triple) agent; his loyalties are questioned by Steeply. The A.F.R. knows Marathe speaks to the U.S.O.U.S., but believes he does so to obtain information for them. Steeply knows Marathe reports back to the A.F.R. At the heart of their conversation is the discussion about where the mysterious film cartridge of James O. Incandenza's final film, entitled Infinite Jest, is located. The film, Infinite Jest, is of interest to both parties, the A.F.R. and the U.S.O.U.S., because it is a lethal piece of media. A few copies had been mailed out anonymously, and upon viewing the tapes, the recipients entered an irreversible state of torpor where all they are able to do or want to do is watch the tape on repeat.
Agent Steeply travels to Arizona, where Orin Incandenza plays professional football, and interviews Orin under the guise of writing a profile about him for Moment, a tabloid-esque magazine. Steeply disguises himself as Helen Steeply, dressing as a woman and wearing prosthetic breasts. The real reason Steeply interviews Orin is to gauge whether he knows the whereabouts of the film Infinite Jest and to learn as much about the Incandenza family as possible, even suspecting that they may be somehow involved in Quebecois separatism (Avril Incandenza is a Quebecois Canadian citizen). Orin calls Hal several times to discuss his new infatuation with the reporter who's following him around for a soft profile.
The story's two worlds—the tennis academy and the halfway house—overlap throughout the novel. The physical proximity of these environments helps. But the thematic elements of the E.T.A. and Ennet House experiences, particularly substance abuse and the concepts of fanaticism and devotion, lend themselves to distinct parallels. Joelle van Dyne a.k.a. Madame Psychosis is Orin Incandenza's ex-girlfriend. Joelle stars in James Incandenza's film, Infinite Jest, and she wears a veil to cover her face, which has allegedly been deformed since her mother, in an attempt to hit her, Joelle's, father, missed and threw a bucket of powerful acid on Joelle's face. Joelle wears the mask as a member of the Union of the Hideously and Improbably Deformed, but it is unclear whether the acid story is actually true. Before the acid attack, Joelle was considered hypnotically beautiful, as in, her beauty has a deleterious effect on those around her. She renders people totally unable to communicate with her beauty. The accounts that she hides her face because it is deformed by acid exist alongside accounts that say she hides it because she is too distractingly beautiful. Wallace never tells the reader in plain terms which is true.
Joelle enters the main narrative in the Y.D.A.U. when she overdoses on crack cocaine in an attempt to end her own life. Joelle's character is a key fulcrum of overlap in the Enfield/Ennet/Quebecois plot triangulation. The novel largely eschews plot and focuses on the emotional and philosophical valence of scenes both remarkable and quotidian, the scenes rarely serve the express purpose of moving the plot forward and rather contribute to the feeling of moving through a world that extends almost infinitely in all directions. But the plot's convergence occurs near the end of the novel, when the Assassins Fauteuil Roulants and the U.S. Office of Unspecified Services both frantically search for the master copy of Infinite Jest. The U.S.O.U.S. knows that if the A.F.R. can make copies of the film, they could distribute it in a massive campaign to immobilize the U.S. populace. The A.F.R. goes after Joelle, knowing that she stars in the film. The U.S.O.U.S. gets to her first. Orin is captured by the A.F.R. and it is suggested that he has been the one distributing the cartridges all along to fulfill personal vendettas against the men with whom his mother cheated on his father. Meanwhile, Hal's confidence in his tennis game are on the steep decline as he comes to terms with his addiction to marijuana. The Ennet House has a violent run-in with a Quebecois separatist group when one of its members kills a separatist's dog. The separatists come to Ennet House to kill Lenz, the dog-killer, but Gately steps in as House staff to defend him and ends up in the hospital with an infected bullet wound. The novel ends in a wave of uncertainty, right before what seems to be a building climax, and at that point, the reader is compelled to return to the first chapter once again, to try and piece together what might have happened from Hal's testimony a year later.