L'histoire se déroule en Californie, où l'on découvre deux familles, les Campos et les Mounters, qui se mènent une guerre sans pitié, à grands coups de meurtres, tortures et attentats.
About eight years after a zombie apocalypse, R, a zombie, spends his days wandering around an airport which is now filled with hordes of his fellow undead, including his best friend M. R and M achieve rudimentary communication with grunts and moans and occasional near-words. As a zombie, R constantly craves human flesh, especially brains, as he is able to "feel alive" through the victims' memories he experiences when he eats them.
The film begins with a scene in which the Palestinians and Jews are both snapping, similar to the opening scene of West Side Story. The two parties head in to their own stands and sing about their own family-owned falafel stands, Hummus Hut and Kosher King ("Our People Must Be Fed/Our People Must Be Served"). During the day, Hummus Hut employee Fatima and Kosher King relative David are daydreaming about each other ("When I See Him"). When Fatima rushes to give a customer his forgotten leftovers, she has a chance encounter with David, and they realize their mutual attraction.
In the West Side's Lincoln Square neighborhood in Manhattan, there is tension between an Anglo gang, the Jets, led by Riff, and a Puerto Rican gang of immigrants, the Sharks, led by Bernardo. After a brawl erupts ("Prologue"), Lieutenant Schrank and Officer Krupke arrive and break it up, warning both gangs to cease fighting or pay. Despite the warning, the Jets decide to challenge the Sharks to a rumble for neighborhood control at an upcoming dance.