A military convoy transporting secret cargo from Area 51 collides with a distracted newlywed couple outside Las Vegas. The container ruptures, unleashing an agile, super-strong zombie named Zeus who wipes out the soldiers and turns his gaze toward the city lights. Vegas falls rapidly to the undead outbreak, forcing the United States military to build a giant perimeter wall made of stacked shipping containers to quarantine the entire metropolis.

Years later, former mercenary and war hero Scott Ward is flipping burgers in a diner when billionaire casino boss Bly Tanaka approaches him with a proposition. Tanaka explains that two hundred million dollars sits locked inside an impenetrable vault beneath his abandoned casino resort on the strip. The President has announced a tactical nuclear strike on Las Vegas scheduled for the Fourth of July, giving Scott a narrow window to assemble a crew, crack the vault, and split fifty million dollars.

Scott recruits a specialized crew: his former combat partners Maria Cruz and Vanderohe, helicopter pilot Marianne Peters, German master safecracker Ludwig Dieter, and gun-toting influencer Mikey Guzman. They also recruit Lilly, a scout known as "The Coyote" who sneaks people past the perimeter, who brings along a corrupt camp officer named Burt Cummings. Tanaka sends along his slimy head of security, Martin, to supervise. Scott's estranged daughter Kate, a volunteer worker at the refugee camp, insists on joining after learning a refugee mother named Geeta went missing inside the city.

Inside the ruins, Lilly shoots Burt in the leg as an offering to the Alphas, a coordinated group of intelligent zombies ruled by Zeus and his Queen. Zeus accepts the sacrifice, allowing the mercenaries to pass through the territory. Inside the casino, Dieter works on the complex mechanism of the Götterdämmerung safe while Peters works to repair an abandoned rooftop helicopter. However, the mission unravels when Martin secretly ambushes the Alpha Queen, beheading her to harvest genetic material for Tanaka's true bioweapon goal.

Zeus discovers his decapitated, pregnant queen and roars in fury, mobilizing every zombie in the city for total war. Martin betrays the group, locking them inside, but he is promptly mauled to death outside by an undead tiger named Valentine. The remaining mercenaries fight for their lives against waves of infected. Dieter sacrifices himself by pushing Vanderohe inside the sealed nuclear-safe vault just as Zeus arrives. Scott, Kate, and Peters fight their way to the rooftop helicopter as the military unexpectedly advances the nuclear missile launch timeline.

Zeus catches up with the survivors on the rooftop, leaping into the helicopter as it lifts off. A brutal fight breaks out inside the cabin; Scott manages to shoot Zeus through the head right as the nuclear bomb detonates over Las Vegas. The shockwave hits the aircraft, causing it to spin out of control and crash in the desert.

Kate crawls out of the wreckage to find Peters dead and Scott fatally wounded. Scott hands her the money he managed to salvage, but he reveals a bite mark on his arm. As he transforms into a zombie, Kate tearfully shoots her father in the head before rescue helicopters arrive. Meanwhile, Vanderohe survives the nuclear blast inside the radiation-proof bank vault. He emerges into the scorched ruins with bags of cash, hikes to an abandoned airport, and hires a private jet to Mexico City. During the flight, he feels lightheaded, walks into the bathroom, and discovers a bite mark on his arm, setting up the grim reality that the global apocalypse is about to begin.