During the initial outbreak, Don and his wife Alice hide with fellow survivors in a boarded-up rural cottage. When an infected swarm breaks in, Don panics and flees, abandoning Alice as she screams for help, barely escaping on a motorboat while watching her get overrun.
Twenty-eight weeks later, the Rage virus has burned itself out as the infected starved to death. A NATO force led by the US Army has secured the Isle of Dogs in central London, establishing District 1 to repatriate surviving refugees under General Stone. Don, now working as a district building manager, reunites with his returning children, Tammy and Andy, telling them Alice died quickly without revealing his cowardice.
Longing for keepsakes of their mother, Tammy and Andy sneak out of the secure perimeter to their old home. There, they discover Alice alive in the attic, disoriented and bite-marked. She is an asymptomatic carrier: her blood carries the live Rage virus, but a rare genetic mutation prevents her from turning rabid. Army medical officer Scarlet Ross realizes Alice's blood could hold the key to a cure, which could also be passed down to her children.
Racked with guilt, Don uses his master security pass to visit Alice in quarantine. He begs for forgiveness and kisses her. The virus transfers via saliva, and Don transforms violently within seconds. He brutally executes Alice and attacks soldiers, triggering an immediate containment failure in the densely packed civilian shelter.
General Stone initiates Code Red: soldiers are ordered to exterminate the entire population to stop the spread. Sergeant Doyle, a rooftop sniper, refuses to shoot civilians and helps Scarlet, Tammy, and Andy escape. As military jets blanket London in firebombs and chemical gas, Doyle sacrifices himself by pushing a stalled car through burning wreckage so the group can reach an extraction point.
Scarlet and the children navigate the dark London Underground with a night-vision rifle, where an infected Don ambushes them. Don kills Scarlet and attacks Andy, biting him before Tammy shoots her father dead. Andy does not turn, proving he shares his mother's immunity. Helicopter pilot Flynn rescues the children and flies them across the English Channel.
Twenty-eight days later, Flynn's empty helicopter rests abandoned in France, as a distress call crackles over the radio. A horde of fast-running infected bursts out of the Paris Metro, sprinting directly toward the Eiffel Tower.
