V rezul'tate sobytiy, opisannykh v predydushchem fil'me, epidemiya virusa yarosti unichtozhila prakticheski vso naseleniye Britanii. Neskol'ko vyzhivshikh ukrylis' v zagorodnom dome, no zarazhonnyye vorvalis' i tuda. Don (Karlayl) okazalsya yedinstvennym, komu udalos' ubezhat', brosiv pri etom svoyu zhenu Elis. Spustya 5 nedel' posle nachala epidemii vse zarazhonnyye pogibli ot goloda, 11 nedel' spustya amerikanskiye voyska v sostave NATO vstupili v London, 24 nedeli spustya nachalis' raboty po vosstanovleniyu strany. Osnovnyye sobytiya fil'ma proiskhodyat cherez 28 nedel' posle nachala epidemii. Vyzhivshiye i repatrianty nakhodyatsya v «zelonoy zone» — rayone Londona, nakhodyashchemsya pod zashchitoy amerikanskikh voyennykh. K Donu vozvrashchayutsya deti — mal'chik Endi (Magglton), pomladshe, i devochka Temmi (Puts), postarshe; oni vo vremya epidemii byli na kanikulakh za granitsey. Don so slezami rasskazyvayet im, kak ikh mat' ubili zarazhonnyye, umalchivaya o tom, chto na samom dele yemu prishlos' yeyo brosit' yeshcho zhivoy. Endi khochet zapoluchit' khotya by fotografiyu svoyey materi, i deti taykom prokradyvayutsya za predely okhranyayemoy zony k svoyemu byvshemu domu. Tam oni nakhodyat svoyu mat', ostavshuyusya v zhivykh. Soldaty nakhodyat detey s mater'yu i zabirayut vsekh troikh v zelonuyu zonu. U zhenshchiny nakhodyat sledy ukusov. Vyyasnyayetsya, chto ona yavlyayetsya bessimptomnym nositelem virusa. Amerikanskiy general prinimayet resheniye unichtozhit' potentsial'no opasnogo nositelya, no v eto vremya Don prikhodit k zhene, prosit u neyo proshcheniya i tseluyet yeyo. Vo vremya potseluya virus cherez slyunu perekhodit k Donu, on zarazhayetsya, ubivayet zhenu i vykhodit na svobodu, kusaya vsekh podryad. Posle ob"yavleniya trevogi voyennyye napravlyayut grazhdanskikh v ubezhishche, tuda zhe popadayet i Endi. Don pronikayet v eto ubezhishche i napadayet na lyudey, nachinaya tsepnuyu reaktsiyu zarazheniya virusom. Okhvachennaya panikoy tolpa lomayet dveri i vybegayet naruzhu. Voyennyye nekotoroye vremya pytayutsya nakhodit' i otstrelivat' tol'ko zarazhonnykh, no zarazheniye rasprostranyayetsya slishkom bystro, i general otdayot prikaz unichtozhit' vsekh grazhdanskikh. Endi udayotsya spastis' iz ubezhishcha cherez ventilyatsionnuyu trubu, i on vstrechayetsya so svoyey sestroy i s biologom Skarlet, kotoraya pytayetsya lyuboy tsenoy spasti detey: v ikh krovi navernyaka prisutstvuyut neobychnyye geny materi, vozmozhno skryvayushchiye klyuch k lekarstvu ot virusa. Im pomogayet spastis' snayper serzhant Doyl, i vmeste im udayotsya pokinut' Sobachiy ostrov, vyzhigayemyy voyennymi s samolotov. Za Doylom na vertolote priletayet yego drug, pilot Flinn, no on otkazyvayetsya brat' s soboy detey i Skarlet. V eto vremya ikh atakuyet tolpa zarazhonnykh, kotorym takzhe udalos' ubezhat' s ostrova. Pilot unichtozhayet mnogikh iz nikh vintom vertolota, i oni dogovarivayutsya o sleduyushchey vstreche na stadione Uembli. Voyennyye prodolzhayut unichtozhat' infitsirovannykh, teper' uzhe za predelami «Zelonoy zony». Oni raspylyayut gaz, Doyl i ostal'nyye spasayutsya v mashine, no motor glokhnet i priblizhayutsya ognemotchiki. Doyl vykhodit naruzhu i tolkayet mashinu szadi, avtomobil' trogayetsya s mesta, no podoshedshiye ognemotchiki szhigayut Doyla zazhivo. Skarlet uvodit mashinu iz-pod obstrela pushek vertolota. Doyekhav do metro, Skarlet (s vintovkoy Doyla i priborom nochnogo videniya) i deti spuskayutsya vniz. V temnote oni teryayut drug druga. Ikh nakhodit Don, ubivayet Skarlet i kusayet Endi. Temmi prikhoditsya ubit' ottsa iz vintovki. Ne poddavshiysya deystviyu virusa, no tem ne meneye infitsirovannyy Endi s sestroy dobirayutsya do stadiona, gde Flinn, kotoromu nikto ne uspel rasskazat' ob osobennostyakh ikh sem'i, reshayet podobrat' detey i perevezti ikh cherez proliv La-Mansh vo Frantsiyu. Prokhodit 28 dney. Pokazan pustoy vertolot Flinna, v naushnikakh prizyvy o pomoshchi na frantsuzskom yazyke. Zarazhonnyye lyudi begut na fone Eyfelevoy bashni.

Following the events depicted in the previous film, a rage virus epidemic wiped out virtually the entire population of Britain. The few survivors took refuge in a country house, but the infected broke in. Don (Carlyle) was the only one to escape, abandoning his wife, Alice. Five weeks after the outbreak, all the infected died of starvation. 11 weeks later, American troops entered London as part of NATO, and 24 weeks later, reconstruction work began. The main events of the film take place 28 weeks after the outbreak. The survivors and repatriates are in the "Green Zone"—an area of London protected by American troops. Don's children—a younger boy, Andy (Muggleton), and an older girl, Tammy (Poots)—return to him; they were on holiday abroad during the outbreak. Don tearfully tells them how their mother was killed by the infected, concealing the fact that he had actually been forced to abandon her while she was still alive. Andy wants to at least get a photograph of his mother, and the children sneak outside the secure area to their former home. There, they find their mother, still alive. Soldiers find the children and their mother and take all three to the Green Zone. Bite marks are found on the woman. It turns out she is an asymptomatic carrier of the virus. The American general decides to eliminate the potentially dangerous carrier, but at that moment, Don comes to his wife, apologizes, and kisses her. During the kiss, the virus is transferred to Don through her saliva. He becomes infected, kills his wife, and goes free, biting everyone in sight. After the alarm is raised, the military sends civilians to a shelter, including Andy. Don infiltrates the shelter and attacks people, starting a chain reaction of virus infection. The panicked crowd breaks down the doors and rushes outside. For a while, the military tries to find and shoot only the infected, but the infection spreads too quickly, and the general orders the extermination of all civilians. Andy manages to escape from the shelter through a ventilation shaft and meets up with his sister and biologist Scarlet, who is trying to save the children at any cost: their blood likely contains their mother's unusual genes, possibly holding the key to a cure for the virus. Sniper Sergeant Doyle helps them escape, and together they manage to escape the Isle of Dogs, which is being burned by military aircraft. Doyle's friend, pilot Flynn, arrives by helicopter to pick him up, but he refuses to take the children and Scarlet with him. Meanwhile, they are attacked by a crowd of infected who also managed to escape the island. The pilot destroys many of them with the helicopter's rotor, and they agree to meet again at Wembley Stadium. The military continues to exterminate the infected, now outside the "Green Zone." They spray gas, and Doyle and the others escape in a car, but the engine stalls and flamethrowers approach. Doyle gets out and pushes the car from behind. The car starts moving, but the approaching flamethrowers burn Doyle alive. Scarlet steers the car away from the helicopter's cannon fire. Having reached the subway, Scarlet (with Doyle's rifle and night vision goggles) and the children descend. In the darkness, they become separated. Don finds them, kills Scarlet, and bites Andy. Tammy is forced to kill her father with a rifle. Unaffected by the virus, but still infected, Andy and his sister reach the stadium, where Flynn, who hadn't been told about their family's unique circumstances, decides to pick up the children and transport them across the English Channel to France. 28 days pass. Flynn's empty helicopter is shown, with French-language calls for help coming from the headphones. Infected people are running against the backdrop of the Eiffel Tower.