28 Weeks Later
Late one night, British animal rights activists break into the Cambridge Primate Research Facility to free chimpanzees being used for medical research. The local scientist warns the activists that the chimps are infected with something he only calls "Rage", but the activists disregard him and set a chimp free. It immediately attacks and infects the activists and scientist.
Twenty-eight days later, a bicycle courier named Jim awakens from a coma in the deserted hospital. As he leaves, he discovers London is rife with signs of catastrophe and was evacuated. Jim is soon discovered and chased through the streets by infected people before being rescued by two survivors, Selena and Mark, who rush him to their hideout at the Canary Wharf Station in the London Underground. They reveal that while Jim was comatose, the virus spread uncontrollably among the populace, turning most people into mindless, vicious killers ("the Infected") and resulting in societal collapse, possibly worldwide.
Selena and Mark accompany Jim to his parents' house, where he discovers that they committed suicide. That night, two of the Infected attack the survivors, and when the fight ends they discover that Mark is bleeding and is likely infected. Selena immediately kills him with a machete, explaining to Jim that the infection is spread through the blood and overwhelms its victims in seconds, rendering them deadly to others. She warns that should he become infected, she will kill him "in a heartbeat". As the two journey through the derelict city the next day, Selena rules out intimacy between her and Jim, declaring that only the fight for survival remains. They discover two more survivors, Frank and his teenage daughter, Hannah, holed up in an abandoned block of flats. Invited to spend the night, Selena and Jim privately debate whether they should remain with Frank and Hannah. Jim says they seem like good people, while Selena fears they will slow her down, warning Jim that putting others ahead of one's own personal survival is a sure way to get killed.
The next morning, Frank informs Jim and Selena that supplies, particularly water, are dwindling, and plays them a prerecorded radio broadcast loop transmitted by soldiers near Manchester who claim to have "the answer to infection". The survivors board Frank's cab in search of the blockade and during the trip bond with one another. Selena's steely resolve begins to soften, while Jim's experiences on the trip begin to toughen him up. When the four reach the deserted blockade, Frank is infected when blood drips into his eye from a body entangled in wires above him. As he warns Hannah to stay away, Frank succumbs to the infection but is killed by hidden soldiers, who then commandeer the cab and take Selena, Jim and Hannah to a fortified mansion under the command of Major Henry West. As Hannah grieves, Selena and Jim reach out to each other romantically. Jim discovers that West's "answer to infection" involves waiting for the Infected to starve to death, while giving hope for community survival by forcing sexual servitude on the female survivors. Jim attempts to escape with Selena and Hannah, but is captured by the soldiers, along with Sergeant Farrell, who disagrees with the Major's plan. While Jim and Farrell are imprisoned for the night, Farrell informs Jim that there is no worldwide epidemic, but rather that the island of Great Britain has been quarantined.
The next day, as two soldiers lead the prisoners into the woods to be executed, Selena and Hannah are trapped as the soldiers circle, set to rape them both. The two executioners argue about how to kill the prisoners and shoot Farrell. Meanwhile, Jim escapes as they search for him, at times firing wildly hoping for a lucky hit. Later, Jim observes the contrail of a jet aircraft flying high overhead and realizes that some part of the outside world is still functioning as Farrell implied. After luring West and one of his men to the blockade, Jim runs back to the soldiers' headquarters where he unleashes Mailer, an infected soldier that West kept chained outside for observation. Mailer attacks the soldiers in the mansion, while Jim sneaks around, killing a soldier and maneuvering around the growing number of Infected. Selena, held hostage by the last uninfected soldier, the cruel Corporal Mitchell, is horrified when Jim, covered in blood, bursts into the room and savagely kills the soldier by eye gouging, leading her to believe that he may be infected. Raising her machete, she hesitates before striking; he quips, "That was longer than a heartbeat," and the two kiss passionately. Hannah finds them and mistakenly thinks that Jim is one of the infected, striking him over the head with a vase. After realizing her mistake, the trio run to Frank's cab, only to encounter West, who shoots Jim in the stomach. Hannah commandeers the cab, backs it up to the front door, delivering West to the infected Mailer. She then drives away with Jim and Selena.
Selena and Hannah rush Jim into a deserted hospital, where Selena performs life-saving emergency procedures. Twenty-eight days later, Jim is shown waking up in recovery again, this time on one side of a double bed in a remote cottage. Downstairs, he finds Selena sewing large swaths of fabric when Hannah appears. The three rush outside and unfurl a huge cloth banner, adding the final letter to the word "HELLO" laid out on the meadow. As a military jet flies over the landscape, the Infected are shown lying by the road, dying of starvation. After the jet zooms past the three waving survivors and their distress sign, Selena wonders if the planes saw them this time.
