The novel opens with a description of the haunted thoughts of Delaney Mossbacher, a weatlhy American who lives in Arroyo Blanco Estates in California. Delaney hit a Mexican man, who we will later learn is a man by the name of Cándido Ríncon, with his car while on his way to a recycling center to drop off some bottles and newspapers, and now he cannot get the image of Cándido's face out of his mind, describing his, "red-flecked eyes, the rictus of the mouth, the rotten teeth and incongruous shock of gray in the heavy black brush of the mustache." Delaney admits, to his shame that his first thought was for the car, and his second thought was what this would do to his insurance.
Not until after having these worries does Delaney get out of the car to look for the man that he hit. He can't find him at first, and he begins to think that the whole thing was a setup by a gang. However, he soon finds Cándido lying next to a shopping cart in the bushes with a shopping bag and a packet of tortillas on top of him. He is in very bad shape, with blood seeping out of his mouth, a torn left sleeve and arm, and a shredded left side of his face. In addition to the tortillas, Cándido has a grocery bag which is now torn by pieces of glass and wet with orange soda. It is clear that he is in very bad shape, groaning, barely able to stand and unable to focus his eyes. When Delaney tries to talk to Cándido, he realizes that he is speaking Spanish, a problem since Delaney only took French in high school. Nevertheless, the Mexican understands that Delaney is asking if he needs medical treatment, which he adamantly refuses. Cándido shakily retrieves the tortillas after he stands, and Delaney is full of relief, knowing that the man will survive and will most likely not sue him. He feels so much better that he offers Cándido a ride, again with French and much pantomiming, but all Cándido wants is money. Delaney gives him a twenty dollar bill, and the two men part ways.
Delaney is so shaken up by the incident that he doesn't even remember getting into the car and driving away, missing the turn to his destination several times. As he goes through the motions of dropping off his recyclable materials, he is thinking about the Mexican and how terrible of a condition he left him in. However, as he's wondering what kind of conditions that Cándido is living in and why he was in the middle of Topanga Canyon, he remembers the shopping cart he found next to Cándido and realizes that he must be camping in the valley. This turns his guilt into anger as he imagines the litter and destruction that the Mexican must be leaving behind and the increased risk of the valley catching fire. He tries to tell himself that he is jumping to conclusions but can't convince himself or drive away his anger. He looks around the recycling plant and notices the overwhelming number of latino men, realizing for the first time just how many wandered the streets of LA every day. Delaney leaves the recycling plant to bring his damaged car to the Acura dealership and to the rather annoying man who sold him the car, Kenny Grissom, lying and saying that he hit a dog. Delaney then calls his wife, Kyra, to tell her what happened, admitting that he hit a man, specifically a Mexican. When she asks if he called Jack Jardine, a family friend who happened to be a lawyer, he tells her not to worry - he already gave the man money. Plus, he was a Mexican.
Chapter two opens with Cándido's point of view. He is in extreme pain and trying to recall the details of the accident. He had gone to the far grocery across the road from the valley, where the prices were cheaper and the Italian paisano who worked the counter actually showed him some respect. He went to cross the road again, he remembered, and that was when Delaney, "the pink-faced gabacho," ran him down with his car. Now, he is left to try to limp down into the valley on what is probably a broken left hip and knee. He falls twice, and the second time he does not get up. He hallucinates, going back to a time in Tijuana, Mexico, a time when he had just been robbed, when América, his wife, was sick, and when he was reduced to digging in the trash.
While her husband is collapsed in the dirt, América is on her way back from an unsuccessful attempt to find work in Venice, CA. The day had started out well, with a refreshing walk along the Coast Highway to the bus stop, but from there it had gone downhill. Once in Venice, she could not find the address given to her by the Guatemalan woman and wandered around terrified until a woman helped her find the correct bus back home. Exhausted, sweaty, and still jobless, she journeys back to her and Cándido's camp in Topanga Canyon, making sure that nobody was following her. She finds her husband unconscious on the path and brings him back to camp. Cándido is still hallucinating, remembering an opossum hunting trip with his dad and the death of his mother (who he imagines telling him to, "Go to the devil"). Meanwhile, América takes the twenty dollars given by Delaney and buys aspirin and other basic first-aid materials, along with some food, but despite her best efforts to convince Cándido to see a doctor he refuses, afraid that Immigration, known by the couple as La Migra, will find them. Cándido wakes up in worse condition than before, urinating blood and not remembering who he is or who América is, leaving América frightened and in tears.
Luckily, Cándido's fever drops in several hours, and soon he is lucid again. However, he remains in excruciating pain, needing assistance to relieve himself and dealing with a concussion - there is no way he can look for work. Thus, after several days of treating her husband, América decides to take matters into her own hands and tries to sneak away to the labor exchange, the place where other people such as themselves who are looking for work, no questions asked, congregate. Cándido wakes up as she tries to leave and forbids her to go. The exchange is no place for a woman, he argues. He remembers a twelve-year-old girl who he knew from the dump he lived in in Tijuana who, despite his efforts to protect her, was raped by men very similar to those who populate the labor exchange. However, América confronts him with their lack of food, his inability to work for money, and, when he refused to concede, his own promises to her of the American dream - a house, a yard, and other possessions. Beaten, Cándido reluctantly watches her walk away.
Chapter three begins with a description of Arroyo Blanco Estates, where the Mossbacher family lives. All of the houses in the estate are in the same Spanish Mission style. They all must be painted in one of three shades of white and must have orange-tiled roofs. The community has a golf course, tennis courts, and a country club - in short, it is your typical middle-class American community. Delaney chose the community for its proximity to nature, a plus for his job as the author of the column, "Pilgrim of Topanga Creek," published in the nature magazine Wide Open Spaces. Boyle describes the Delaney's highly scheduled lifestyle, in which he lets out the family dogs, Osbert and Sacheverell, and the cat, Dame Edith, takes in a bit of the morning air, makes breakfast for Jordan and Kyra, the family breadwinner as a real estate agent for Mike Bender Realty, Inc., drives Jordan to school, and then, finally sits down for several hours to write and to hike. The routine even includes a cranky Jordan complaining about the high-fiber, whole grain diet Kyra has him on.
On this particular morning, however, the dogs are barking loudly throughout the morning routine, which Delaney and Kyra dismiss as merely them chasing after a squirrel. However, at precisely 7:32 AM (Delaney is sure to note the time of the disturbance), a shriek of fear draws the frightened Mossbachers into the backyard, where they see a coyote running away with one of the dogs (who turns out to be Sacheverell) in its mouth and jumping over the six-foot chain link fence to escape. Despite Kyra and Delaney's attempts to run after the animal, they are unable to catch up to it, and later, after a distraught Kyra had left for work and dropped off Jordan at school, Delaney finds a piece of Osbert's leg, the only remnants of the poor pet.
Delaney is outraged at this turn of events, since he believes the coyotes were drawn to the neighborhood by people who left food on their driveways for the dog-like creatures, and he decides to attend the emergency meeting of the Arroyo Blanco Property Owner's Association that Jack Jardine, president of the association, called. He intends to talk about the issue of people feeding coyotes, despite the fact that the meeting was called in order to vote on whether or not to build a gate at the entrance of Arroyo Blanco. A heated debate about the gate ensues, with some arguing against it with worries about increased fees and desires to preserve the open nature of Arroyo Blanco, while others, like Jack Cherrystone and Jim Shirley, present cases of crime and theft serious enough to even distract Delaney from his quest for a moment. He is not distracted for long, but when he tries to address the issue, even waving around Osbert's bloody leg to get people's attention, nobody will pay attention to him, and he soon storms out in anger. Once outside, he is questioned by Jack Jardine, Jr., Jack Jardine's son, about the Mexican that he hit with his car and where the incident occurred. Although Delaney finds this very odd, he dismisses it and returns home, the coyote issue still on his mind.
The Tortilla Curtain is divided into three parts, each with eight chapters. Boyle switches back and forth between the Rincóns and the Mossbachers in an attempt to make their lifestyles as easy to compare and contrast as possible. This method will prove to be very effective in highlighting the most shocking as well as the most ridiculous aspects of each of the families' lives. Part I is called "Arroyo Blanco," the name of the neighborhood in which main character Delaney Mossbacher and his white, middle class neighbors live, and it begins with a literal crashing together of two worlds. This accidents brings together these two very different men and thus sets off a chain of events that will have profound effects on both of their lives. In the present, however, it simply reveals the true values of Delaney who, though he claims to be very liberal and equally caring of all people, is content to give a seriously injured Cándido twenty dollars in exchange for just walking away and not trying to get insurance benefits out of him. His salesman at the dealership even compares hitting a Mexican man to hitting a dog on the road - it is unfortunate but there are no serious consequences or reasons to be worried. The experience will still haunt Delaney, however, because he has been forced to interact with one of these Mexican immigrants, whom he usually ignores on a day to day basis, on a very personal level. The invisible wall between white people and Mexicans has been breached, and it is at this point that his carefully assembled, real-world ignorant values will begin to fall apart.
Chapter two introduces readers to the shocking lifestyle of Cándido and América, and they see that they live like the animals that Delaney is so fascinated with, truly becoming a part of nature in order to survive. A badly injured Cándido retreats within himself and thinks back to his past in Mexico, a tendency that will recur anytime Cándido or América is undergoing great stress or pain. These two tend to retreat within themselves, walling themselves off from the world and taking comfort in memories of home, a technique which Cándido learned from his father at a young age. Another important insight into Cándido's character is his shame at having to let América work to earn money. He is a man's man, and the thought of his woman providing for him shames him greatly. This is very different from Delaney, who actually has no problems taking on a very homebody-type role in his household. This difference may simply reflect the different cultures that these two come from.
The description of Arroyo Blanco introduces readers to Boyle's portrayal of the middle-class American lifestyle. The community is highly ordered and follows the letter of the law, wired to prevent any chaos from overtaking the residents and ruining their strictly scheduled lifestyles, such as the one that Delaney leads. This order is centered around their jobs, which explains why it is lacking in the lives of Mexican immigrants like América and Cándido, who cannot get stable jobs. Another interesting detail presented is the strict high-fiber diet that Kyra has her son Jordan follow. This ties into what will be the recurring theme of food. Despite the added expense, Kyra chooses to have her son on this diet for his health no matter how much he protests - money is not an option. The Rincóns, on the other hand, have to make do with what their meager salaries can afford.
The appearance of the coyote introduces one of the most important parallels in the book - that between the coyotes and the Mexican immigrants. The coyote hops the fence with no problems go after the family dog, or what it sees as a piece of meat that can feed its family. In a similar way, many Americans see immigrants as "dogs" who hop the fence and then steal jobs and taxpayer-supported public services before running back to Mexico with their earnings. The similarities between the two will continue, and it will be important to focus on peoples' attitudes towards the cunning coyotes. They will greatly reflect their feelings regarding Mexican immigrants in their hometown.
Finally, the characters of Jack Jardine and Jack Cherrystone will also be important characters to pay attention to in the future. These men, highly respectable in many ways, will represent the voice of the white middle class, a role reflected in details about them. Jardine is the president of the Arroyo Property Home Owner's Association - thus, he is basically the voice of Arroyo Blanco, a white middle-class sanctuary. Cherrystone, on the other hand, uses his booming, distinctive voice to make trailers in Hollywood, thus literally making him the voice of Hollywood. However, "Hollywood" can be loosely interpreted as LA, making him the voice of LA throughout the novel.