The United States is devastated by a mysterious which reanimates recently deceased human beings as -eating . Despite the best efforts by the U.S. government and local authorities to control the situation, millions of people are killed and reanimate; social order is collapsing. Some rural communities and the military have been effective in fighting the zombie hordes in open country, but urban centers are helpless and largely overrun. Confusion reigns at the WGON television studio in Philadelphia by the phenomenon's third week, where staff members Stephen Andrews and Francine Parker are planning to steal the station's traffic helicopter to escape the city. Meanwhile, police SWAT officer Roger DiMarco and his team raid a where the residents are defying the of delivering their dead to National Guardsmen. Some residents fight back with handguns and rifles, and are killed by both the overzealous SWAT team and their own reanimated dead. During the raid, Roger meets Peter Washington, part of another , and they partner up together. Roger tells Peter that his friend Stephen intends to steal his workplace's helicopter and flee, and suggests that Peter come with them. They are informed of a group of zombies trapped in the basement, which they assist in the grim job of destroying.
That night, Roger and Peter rendezvous with Francine and Stephen and leave Philadelphia in the helicopter. Following some close calls while stopping for fuel, the group comes across a shopping mall, which they decide to make their sanctuary. Francine reveals that she is pregnant. Peter offers to abort the child, but this is rejected. To make the mall safe for habitation, they block the entrances with trucks to keep the undead masses outside from building up enough cumulative force to break through; they also craft a wooden "false wall" to hide the access to their living space. During the blockade operation, Roger becomes reckless and is bitten by the zombies. After clearing the interior of zombies, the four are able to enjoy a hedonistic lifestyle with all the goods in every store available to them. Roger eventually succumbs to his wounds, soon reanimates and is shot in the head by Peter. After several months, all emergency broadcast transmissions cease, suggesting that the government has collapsed and a large portion of the population has been killed and reanimated. Stephen also teaches Francine how to operate the helicopter in case of emergency.
A gang of nomadic motorcyclists, having seen the helicopter during one of Francine's flying lessons, break into and start looting the mall, destroying the barriers and allowing hundreds of zombies inside. While Peter suggests they let the bikers take what they want and move on, Stephen foolishly starts a gun battle with the bikers and is shot in the arm. He tries to escape through an elevator shaft, but is cornered by the undead and bitten several times. As some of the bikers, shot by Peter, are consumed by the zombies, the rest retreat with their stolen goods. A reanimated Stephen, apparently conscious enough to remember the false wall, breaks through it and leads the undead to Francine and Peter. As Stephen enters their hideout, Peter kills him while Francine escapes to the roof. Peter then locks himself in a room and contemplates suicide. When zombies burst into the room, he has a change of heart and fights his way up to the roof, where he joins Francine. The two then fly away in the partially fueled helicopter to an uncertain future.