The following version of this book was used to create this study guide: Alam, Rumaan. Leave the World Behind. New York: Ecco, 2020.

Leave the World Behind begins with a couple named Clay and Amanda and their teenage children Archie and Rose arriving at the secluded house on Long Island they have rented for their vacation. They are an ordinary white, upper-middle-class family from New York. Clay is a professor at City College and Amanda is an advertising executive. They pass an ordinary first day, buying groceries for the house and swimming in the pool. The next day, the family goes to a nearby beach, then returns to the house for dinner. The children go to bed, and shortly thereafter, Amanda and Clay hear a knock at the door.

They are both frightened, but Clay answers the door to find a black couple in their 60s on the other side. They introduce themselves as G.H. and Ruth Washington. They are the owners of the vacation house and they have driven in from Manhattan. There was a blackout in the city and it scared them so they fled to Long Island. They ask if they can stay the night in the house. G.H. offers to repay part of their rental fee. Amanda checks her cellphone and sees a news headline about a blackout, but then her phone loses service. She asks to speak to Clay privately.

Amanda tells Clay she does not believe the Washingtons really own the home; her suspicion is primarily due to her disbelief that a black couple could be wealthy enough to have a nice vacation house. Clay reassures her and insists that letting them stay is the right thing to do. She finally agrees and they return to the kitchen where they talk with the Washingtons about what might have caused the blackout. Shortly thereafter, Ruth and G.H. retire to the finished basement to go to bed. They worry about their adult daughter, Maya, who lives in Massachusetts with her wife and their twin sons.

In the morning, Amanda wakes to Rose complaining that the television is not working. Clay tells Rose to go outside, and when she does, she sees dozens of deer in the yard. The adults talk about their lives back in New York City; Clay and Amanda are surprised to learn that the Washingtons live on the Upper East Side, a very posh Manhattan neighborhood. G.H. is a financial analyst and Ruth once worked in the admissions office of a prestigious high school, though she is retired. Since the phones and televisions are not working, Clay offers to drive into town to see if he can learn any information about the blackout. However, without the GPS on his phone, he quickly gets lost.

While Clay is gone, Amanda and the Washingtons sit by the pool, and Archie and Rose go swimming. The children wander off into the woods where they find an empty shed, and then further in, a brick house. Driving around aimlessly, Clay comes across a woman on the side of the road. He pulls over but discovers she only speaks Spanish. She begins to cry, and Clay, having no idea what she is saying, feels frightened and drives away. Meanwhile, in the city and across the country, the massive power outage leads to numerous deaths and general pandemonium.

Back at the pool, Amanda and the Washingtons suddenly hear an incredibly loud noise that cracks the sliding glass door of the house. The narrator notes that it is the sound of military aircraft flying out of New York, off to intercept an unnamed threat en route to the country's eastern shore. However, the plane mistakes a passenger plane for its target and shoots it down, killing 400 civilians. Panicked, Amanda runs to find the children. Clay, who has also heard the noise, returns to the house. He does not tell the others that he got lost, nor does he mention the Spanish-speaking woman.

As the group tries to regain their bearings, Archie comes down with a fever and vomits. Ruth takes his temperature and gives him Tylenol. Clay and Amanda go to bed and have sex. Afterward, they get in the jacuzzi and G.H. joins them. They hear a splashing sound and discover a flock of flamingos in the swimming pool. Suddenly, the loud noise recurs. The children come running from their bedrooms. When the noise stops, Clay, Amanda, Rose, and Archie all go to bed in the master bedroom. When the children fall asleep, Clay and Amanda wonder whether they should try to return to the city in the morning to get Archie to a doctor.

When they awake in the morning, five of Archie's teeth fall out. The adults determine that they need to get him to the town's hospital immediately. G.H. offers to drive. Then they realize that Rose is missing. Panicked, they split up to search the house and the grounds. In the yard, Archie suddenly feels ill again and vomits. They decide G.H. will drive Archie and Clay to the hospital while Ruth and Amanda continue searching for Rose.

On the way to the hospital, G.H. decides to stop at the home of the contractor who remodeled the vacation house, Danny. He thinks Danny will be able to help them, but when they arrive, Danny sends them away. Back at the house, Ruth tries to reassure Amanda that they will find Rose.

Rose had awoken that morning and decided to return to the brick house in the woods, hoping its owners would be present. They are not, but Rose finds some useful supplies. The narrator notes that Rose, unlike the vast majority of people, will survive the apocalypse that is unfolding throughout the world. She thinks about the future and imagines herself doing chores and daily activities at the vacation house with her family and the Washingtons.