Gerry Lane is a former UN employee who lives with his wife Karin and his two daughters in Philadelphia Pennsylvania. One day while stuck in traffic, they notice many helicopters and policeman passing by for some reason. When one of the policemen on motorcycles zooms by and breaks off the car's side mirror, Gerry goes out to pick it up, only to notice an explosion in the distance. A policeman tells him to get back in his car when he is suddenly hit by a zooming truck that crashes through the cars. Gerry panics and zooms his car behind the trail of the truck. Everyone in the city starts running and panicking. They're car crashes in the city square and Gerry can hardly hear from the crash, as he exits in the confusing chaos, growls can be slightly heard. When his hearing comes back, he sees people being attacked by people that appeared to be cannibalistic and insane. They appeared to be zombies. He and the family try to run. As they are, Gerry notices a man being bitten by one of the infected, and in just 12 seconds, he becomes a zombie. He and the family get on an RV and leave the city. The view shows the whole of Philadelphia being overrun by zombies as well as other cities worldwide, showing that there is a violent plague that somehow turns people into a zombified state.
As they drive away, Gerry gets a call from an old friend named Thierry Umutoni, a UN deputy Secretary General who could be seen escaping New York. The Lanes go to Newark New Jersey and get supplies from a store. At night, they run from the zombies into an apartment building and take refuge in an apartment with a boy Tommy and his two parents. Over the night, Thierry organizes a helicopter to pick up Gerry in the morning. Once morning hits, they leave the room and run through the violent zombies to the roof where the helicopter arrives. Tommy's mom dies and his dad is zombified. The lanes and Tommy escape to a U.S Navy Vessel in the Atlantic where scientists and military personnel are analyzing the world wide zombie outbreaks. A man named Fassbach says that the plague is a virus and that the development of a vaccine depends on finding the origin. Gerry must help him find the source of the outbreak since he says his family will be removed if he does not come. Gerry says goodbye to his family before he and Fassbach fly to Camp Humphreys, a military base in South Korea. They find out that the infection was introduced to the base by its Doctor, who was ultimately incinerated by a soldier with a lame leg that the infected ignored. They also meet an imprisoned CIA Operative who sold weapons to North Korea (to help fight the infection) He tells them that there is a safe zone in Jerusalem that has been maintained by the Israeli Mossad since before the outbreaks official acknowledgment. As they try to shoot the zombies outside and try to get on an aircraft, Fassbach slips and accidentally shoots himself dead. Only Gerry and the pilot make it out alive and fly to Jerusalem.
Gerry meets Mossad Chief Jurgen Warmbrunn, who says that months earlier he intercepted an Indian military message claiming that Indian troops were fighting the zombies, which they called "Rakshasa". Israel had quarantined Jerusalem, erecting huge walls all around it to create a safe zone allowing survivors to take refuge. As they're in the open next to the walls, many citizens gather and start singing and the loudspeaker poles have loud sounds going all over. As this is heard, outside the walls, the zombies start running to the wall. They climb on top of each other and form a zombie pyramid that goes up and successfully climbs over the wall. The zombies fall down below and the soldiers immediately start shooting at them and the zombies relentlessly chase the running people. Juergen Orders some Israeli soldiers to escort Gerry back to his plane. Gerry and the soldiers run from the zombies and through the terrified people. The helicopters try to shoot the zombie pile and the zombies in the city. As they are running, Gerry notices zombies ignoring an old man and an ill boy completely. Gerry and the soldiers run through an alley and then one of the soldiers is bitten on the hand by a zombie. Thinking fast, Gerry chops off the hand and wraps around bandages quickly. The soldier's name is Lieutenant Segen. Gerry carries her and runs to the airport where they board a commercial airliner and take off.
Gerry looks through the window and watches in horror as all of Jerusalem becomes a zombified infestation. He tries to keep Segens's handless arm in bandages during the flight. He is also contacted by Thierry who tells him that the plane is going to a World Health Organization (WHO) Facility outside Cardiff, Wales. When they're almost there, a single zombie is shown to have stowed away onto the plane and turns the rest of the people on board into zombies. After an unsuccessful attempt to block off the doors leading to the section of the plane with the uninfected, Gerry grabs a grenade and blows a hole in the plane that sends all the infected out into the open. The plane crashes and Gerry is knocked out. When he wakes up, he is barely able to move because he has a piece of metal impaled on the right side of his stomach. He and Segen limp to the Who Facility where Gerry passes out. He awakes 3 days later to several WHO doctors in an area of the WHO Facility that isn't overrun with zombies. He explains to them his theory that the zombies don't attack seriously injured or terminally ill people since they would be unsuitable hosts for viral reproduction. He suggests that they test this by infecting somebody with a pathogen from the facility, but the pathogens are stored in a wing that has zombies near it. Gerry, Sagen, and the lead WHO Doctor sneak there way pass the zombies, knowing that they can be attracted by sound. When they make an accidental sound, the zombies start chasing them, and Gerry is separated. The other two escape back to the safe part of the building while Gerry finds the pathogen vault. He goes in and finds the bin with the vial. But as he turns to leave, he sees a zombie is behind the door trying to get in. Gerry decides to inject himself with an unknown pathogen to test his theory. He waits many minutes for the pathogen to take effect. Then he opens the door to find the zombie completely ignoring him. He exits the room and creates a loud noise using a soda machine. As the other zombies run towards Gerry's direction, they all ignore him and he makes it back safely. Gerry has found the type of "zombie camouflage" that can be used for survivors. Later, he is brought back to his family and they hug. Different scenes show how cities worldwide are lost and that the zombie camouflage has bought survivors some time. Gerry says that this war is far from over and they still don't know how it started. He says "Our War Has Just Begun."