In the Bergen Refugee Camp in Norway, Selena is visited by Clint Harris, an American journalist and war correspondant. Clint explains that he and his team are going on an expedition into quarantined Britain to London (to investigate the rumours that a US-led NATO force will repatriate London), and he wants Selena to act as a guide for them. At first, Selena refuses and tells Clint to go away, but then she examines her old necklace, and, remembering when she was happy with her husband, David, decides to go after all. She joins Clint at his helicopter, where Clint introduces her to his team: Derrick, Trina, Hirsch, Acorn and Randall. Selena takes a quick dislike to Derrick and vice versa. Clint explains to Selena that they will land in Sumburgh on the Shetland Islands, where a boat will pick them up and take them to mainland Scotland, where the quarantine is weak enough for them to slip past. From there, they will make their way across the country to London.
However, on the way, the American military patrolling the airspace around Britain shoots at their helicopter, forcing them to land on the Islands approximately nine miles from Sumburgh. There, when Hirsch is attacked by two Infected, but saved by Selena, the group realise that the military were shooting at them because the Rage Virus has recently spread to the Shetland Islands.
The group take cover in a hotel from the Infected, but Clint warns them that if they miss their boat, they will be left marooned on the infected island. So Selena and Derrick go out into the car park, which is swarming with Infected, and Derrick hotwires a van while Selena holds the Infected off. Meanwhile, back in the hotel, Hirsch and Trina go off searching for weapons, and come across a lift shaft filled with Infected. When Hirsch accidentally disturbs the Infected, he and Trina run back to the group at the front of the hotel, followed by the Infected. Derrick then rams the van into the hotel through the front doors, and the group get inside and narrowly escape the Infected. Derrick drives the group to Sumburgh, but they find their boat has not yet arrived, so they decide to hold up in a pub for the night until their boat arrives at dawn.
In the pub, Randall starts a game of Texas Hold'em Poker with Trina and Acorn, and Selena and Derrick sort out their differences over a drink, then join the game. Just then, Hirsch comes in, being attacked by an Infected, which Selena immediately kills. It is then shown that Hirsch was bitten on the arm, and he admits that he is infected. Despite Trina's pleas, Selena then kills Hirsch with her machete for the safety of the rest of the group. Selena warns the horrified group of the peril they're in, and orders them to prepare for an attack, as more Infected will be coming.
As the group barricade the doors and windows, Derrick reminds Clint that Trina and Hirsch were in a relationship, and warns him that Trina will likely try to get revenge on Selena. Eventually, the Infected come and attack the pub, but the group try to hold them off. During the attack, Trina (having become psychotically obsessed with getting revenge on Selena for killing Hirsch) bites Selena in a bid to frame her as infected. However, before the rest of the group can kill her, Selena proves that she isn't infected, and then confronts Trina. The group's boat then arrives, and they escape aboard, pursued by a horde of Infected. They are greeted by Harlan, the sea captain of the boat, and an old friend of Clint's.
On the way to Scotland, they find the US Navy waiting for them, protecting the quarantine. However, Harlan is able to get them past. But near the shores of Scotland, an American jet comes and blows up the boat, killing everyone but Clint, Selena and Derrick; the latter is blinded by the explosion. Selena then has another flashback to her life with her husband before the outbreak, this time of when their cellar flooded. After Selena, Clint and Derrick meet up, they swim to shore and set up camp. Clint and Selena discuss what to do with Derrick; Selena wants to euthanize Derrick, as he will slow them down due to his blindness, but Clint refuses to allow it and Selena reluctantly agrees.
The next chapter acts as a prologue to the series; one day, Clint's editor, Eliott Muniz, calls him to inform him of the Original Outbreak in Britain. Clint decides to cover a story about it, and finds his colleague and best friend, Derrick, in a pub and convinces him to come with him to Britain. They arrive at JFK Airport, and encounter a stampede sparked by paranoia of Infection reaching America, as well as a soldier who violently tries to confiscate Derrick's camera. They successfully board a plane for Stansted Airport, England, but it gets diverted to Frankfurt, Germany, when mainland Britain is quarantined during the journey.
Approximately a month and a half later, Clint and Derrick arrive in Berck, France, where they meet Clint's old friend Major Sanders. Clint and Derrick want to see the Rage Virus up close, so Sanders takes them to an American research facility in Newport on the Isle of Wight, where he shows them a military scientist exposing an Iraqi war criminal called Ahmed Karzaii to the Rage Virus. When an accident with a syringe results in the scientist becoming infected, Sanders orders Clint and Derrick to return to France immediately. Back in France, Clint and Derrick discuss going to London, and Derrick decides to go to one of the "Manchester Three" (Jim, Hannah and Selena) to guide them through infected territory.
Back in the present time, in the morning, Clint and Selena are chased through the woods by two Infected, which almost kill Derrick before Selena kills them. The trio realise from this encounter that the reports that the Infected in mainland Britain had starved to death were not accurate. The group take refuge in a rural house from the Infected as night falls, and Derrick falls sick from an infection in his wounds. Selena tries again to convince Clint that they should kill Derrick, but Clint refuses. The next day, Clint and Selena decide to take Derrick to Halkirk to find antibiotics for his infected wounds. They arrive in a nearby village and try without success to hotwire a pickup truck. When a storm comes, they decide to stay in the back of the pickup for the night. At night, Selena has another flashback to her life with David before the outbreak, this time of when David tried to fix their electricity.
Back in the present time, a horde of Infected come at night, and when Derrick accidentally alerts them, they attack and wreck the truck, but give up and leave before they find the trio. The next day, Clint tries again to hotwire the pickup, this time with success, and the trio drive through the countryside towards Halkirk. But on the way, they are stopped by a trio of survivors, led by Gordon. After Selena violently confirms to Gordon that she and Clint aren't infected, Gordon and his gang take them to see their leader, Kate, at their safe house. Kate is at first reluctant to take Derrick in, as resources are already dwindling, but she eventually decides to keep Derrick safe while Clint and Selena go to Halkirk for antibiotics. However, she also warns them that she has sent many members of her group of survivors to Halkirk, and none of them have ever returned. Clint agrees, and he and Selena travel to Halkirk on foot. Along the way, Clint and Selena argue over Clint's decision, and Clint tries to get more information about Selena's past out of her (to no avail).
Meanwhile, back at Kate's house, Kate talks to her son, Douglas, over a walkie-talkie, and reveals that she is sending Clint and Selena to Halkirk to rescue him. Clint and Selena reach Halkirk, to find the town deserted and destroyed. They enter what Kate described as the chemist's shop, but only find Kate's young son, Douglas. Selena is furious that Kate tricked them, and decides to return with Douglas after they raid Halkirk's real chemist's. As night falls, hordes of Infected come and break into the building, forcing Clint, Selena and Douglas to escape into a back alley. They are able to slow the pursuing Infected down by running up a catwalk and then collapsing it, although Douglas falls off into a street below in the process. Selena saves Douglas from the Infected, and the two narrowly escape back onto the catwalk.
The trio jump from rooftop to rooftop to avoid the Infected in the streets, until they reach the chemist's. After collecting what they need, the Infected attack the chemist's. Back at Kate's house, when she hears Douglas scream over the walkie-talkie, she prepares to murder a sleeping Derrick, but one of the survivors that are holed up there tries to reason with her to wait a little longer. Back in Halkirk, Selena, Clint and Douglas are chased through the streets by the Infected, but are able to escape them by swimming across a river. The Infected try to follow the trio through the waters, but are unable to swim, and are caught in the river and drown. Clint and Selena return to Kate's house with Douglas and the antibiotics Derrick needs, and Kate and Douglas happily reunite.
Once Derrick gets better the next day, he, Clint and Selena prepare to leave. Douglas, blaming Kate for his father's death, refuses to stay with her, and tries to get Selena to let him come with them. At first, Selena refuses, but when Douglas decides to leave into the wilderness on his own, Selena reluctantly lets him come with them. After the four narrowly avoid being found by a CIA squad led by Captain Stiles - a former officer in the British Army - they realise they are being hunted. They later notice a squad of American Black Ops soldiers travelling on the road, and head through the woods in search of shelter for the night. They find an old hut in the woods and try to spend the night in there. However, the Black Ops soldiers arrive in search of Infected to capture and take back to their base, then leave with several captive Infected.
Moments later, a forest fire started by the Black Ops soldiers comes, along with dozens of Infected fleeing the flames; forcing Clint, Douglas, Selena and Derrick to escape through the woods. They are found by the Black Ops soldiers, who are openly hostile and take them back to their camp. The soldiers detain Selena, Clint, Douglas and Derrick, and knock Selena out for attacking Dr. Billingsworth, a scientist at the camp who is researching the Rage Virus. While she is unconscious, Selena has another flashback to her life before the outbreak, when her neighbour, Kirk, offered her gardening tools to help her cut a hedge. Among the tools were the machete that Selena now wields. After Selena wakes, two soldiers take her to see Billingsworth, who, upon discovering who Selena is, orders she be kept alive to be given to Captain Stiles. Billingsworth explains to Selena that he is attempting to modify and weaponise the Rage Virus. He then has Douglas brought in, and injects him with the virus as an experiment while a horrified Selena watches.
Selena is locked back up with Clint and Derrick, while Billingsworth keeps the infected Douglas alive for observation. A soldier arrives and informs Billingsworth that the forest fire is approaching the camp. Billingsworth decides to evacuate the camp, but leave Selena behind to either be captured by Stiles when he arrives, or killed by the fire. A soldier tries to take Clint and Derrick to Billingsworth before he evacuates, but the men and Selena restrain and kill him, and escape detainment. Clint and Derrick go to the edge of the camp to meet Selena there, while she, in the meantime, goes back to Billingsworth's lab. At the lab, Billingsworth is informed that the camp is ready for evacuation. Just then, Selena breaks into the lab and gives the infected Douglas a mercy killing. She then takes revenge on Billingsworth for infecting Douglas by splashing Douglas's infected blood in his eyes and then leaving the infected Billingsworth trapped in the lab to rage and die. Selena meets up with Clint and Derrick, and after Selena releases the captive Infected onto the camp, they escape in a Humvee. The remaining personnel, meanwhile, try to evacuate via helicopter, but are attacked and slaughtered by the released Infected.
After escaping the camp, Selena, Clint and Derrick abandon the Humvee (as it has a flat tire), and take an abandoned sportscar with which to get to London faster. On the way, the trio lose the sportscar when it falls down a collapsed part of a bridge, and continue on foot. They reach Inverness and decide to commandeer a train from there on their journey to London, but find that the train is swarming with Infected. The trio lock themselves from the Infected in the driving cart, and Derrick sacrifices himself decoupling the passenger carts the Infected are in, leaving Clint devastated.
After the train reaches Edinburgh, Clint and Selena mourn Derrick at a deserted tavern, before continuing to travel by foot through the dilapidated streets of Edinburgh. In the streets, the duo are ambushed by two survivors, Paul and Angus, but they are able to overpower and escape them. Meanwhile, in the countryside between Inverness and Edinburgh, Captain Stiles fires on the carriages that were separated from the train Clint, Selena and Derrick commandeered. After inspecting the carriages and finding Derrick's remains among the dead Infected, Stiles sets off in search of the remaining two. Back in Edinburgh, Clint and Selena are chased and captured by the survivors of Edinburgh, led by Raj. Raj explains that they have food and electricity in Edinburgh, but are under the tyrannical rule of "the King", and are at constant war with Glasgow over resources.
Raj takes Clint and Selena to see King Dixon, and his queen, Minnie, the tyrannical rulers of the "Kingdom of Edinburgh". Dixon and Minnie take Clint and Selena's vitamins and one of their guns, and Selena's earrings, to pay for the alcohol the two drank at the tavern. As punishment for breaking Paul's arm, Dixon then has Selena put in the "Mannequin" for the night (in which Selena will be put in a cage in the streets for the night, surrounded by Infected, and must stay exactly in the centre of the cage in order to stay out of the reach of the Infected through the bars). Meanwhile, Raj visits Clint, and asks where he and Selena came from. Clint explains that he is an American journalist who is covering a story about the Rage Virus, and also reveals that the rest of the world outside of Great Britain is continuing normally.
Meanwhile, in the Mannequin, Selena has a hallucination of David, Douglas and Derrick, as well as Mark, Frank, and Clint's deceased team. She wants to just let her life end and be with David, but the hallucination of David convinces her to stay alive. Edinburgh then comes under attack by Glaswegians who free Selena, and a fight ensues. After taking her earrings back from Minnie, Selena reunites with Clint and flees Edinburgh in a stolen car with him, leaving the peoples of Edinburgh and Glasgow to fight to the death.
Clint and Selena keep driving south, across the English border, until their car eventually runs out of petrol in rural northern England, forcing them to continue on foot to London. They come across a giant peach tree, and rest under it for a while, until they see an American jet flying overhead. They travel to a rural farmhouse, where they find supplies and a working pickup truck, as well as an infected man dying of starvation. Using the pickup from the farmhouse, Clint and Selena continue to drive south; arriving in a deserted village, devoid of life and also free of Infected (with most of the Infected south from Scotland having starved to death). They find a video message by a man named Charles to his wife, Janice, from during the initial outbreak.
Clint and Selena spend the night in the house, and each have a warm bath. The next day, Selena fears that she and Clint are being watched, so the two try to leave in the truck they arrived in, but find that the keys have been taken. They hide in the bushes until nightfall, waiting for their hunter to show himself, when the two see Captain Stiles inside a house. They use the light from a burning TV inside a house as a decoy while they steal Stiles' car and flee the town in it. Stiles chases Clint and Selena in his Hummer, but the two escape the Captain when Clint shoots one of his Hummer's tires. The next day, Selena takes Clint to an abandoned town in Cumbria to treat a gunshot wound Stiles gave him during the chase, and as the two wander the town, they come across a wall covered in missing people's posters.
A US military squad led by Sergeant Luis Rodriguez then arrive by jeep, and Clint and Selena (mistaking the jeep for Stiles' Hummer) try to flee until they realise that it is not Stiles. Luis offers to take Clint and Selena to District 1 in London, when Captain Stiles arrives and murders Luis and his entire squad. Clint and Selena hide from Stiles in a building, and while Clint takes one of the dead soldiers' guns, Selena lures Stiles out. Stiles follows Selena into a building filled with infected corpses, and Selena evades him by hiding amongst the dead Infected and disguising one of them as her. Clint picks Selena up in Stiles' stolen Hummer, and as night falls, the two drive to a dock. After dumping Captain Stiles' Hummer into the water, they sleep aboard a boat for the night.
That night, Captain Stiles, who has followed them, comes aboard the boat and forces Clint to jump overboard. Stiles then reveals that he is after Selena because he was good friends with the late Major Henry West, and blames Jim, Hannah and Selena for West's death. Stiles takes Selena hostage and returns to shore with her. Clint, having escaped to shore as well by holding onto the side of the boat as it returned to the dock, climbs onto the dock and passes out. The next morning, Clint is found by a military squad led by Dog, who believe that Clint and Selena are the ones who killed Sergeant Rodriguez and his squad, and demand that Clint tell them where Selena is.
Captain Stiles travels with a captive Selena towards Manchester. When Stiles' car runs out of petrol, he continues with Selena on foot. On the way, Stiles forces Selena to carry everything for him, and Selena enrages Stiles by calling Major West a monster and a rapist. Meanwhile, Dog and soldier Brad discuss Clint's story about Captain Stiles, and decide to find Selena and take them to District 1 if Clint's story proves to be true. Stiles and Selena arrive in Manchester, and travel through the scorched ruins of the city. Clint and Dog's squad also arrive, and search the ruined city for Stiles and Selena, but fail to find them.
Stiles takes Selena to the Worsley House where Major West and his men died, and forces her to show him West's body and explain how he died. Selena then breaks free and crawls over to West's decomposing corpse. She takes West's dog tags and throws them into the lawn outside the mansion, which, unknown to Stiles, is laced with landmines. As Stiles goes across the lawn to retrieve Major West's dog tags, he steps on a landmine, blowing him to pieces. Clint and Dog's squad then arrive and rescue Selena.
Dog takes Clint and Selena to District 1, which is being repopulated by NATO with British refugees under American supervision. There, Clint and Selena quickly fall in love, and begin to settle into a quiet, peaceful life. Clint also befriends fellow residents Charles and his wife Janice, and contacts his editor, Eliott, in America to tell him that he is alive and wants Eliott to begin printing his story as soon as he and Selena get to New York. One morning, Selena sneaks out of the green zone and across London to her and David's old home. Back in District 1, when Clint hears that the military have captured the people that have snuck out of the green zone, he fears that Selena is among them, until he discovers that it is only Tammy, Andy and Alice Harris from 28 Weeks Later. After entering her old London home for the first time since the original outbreak, Selena has another flashback. It is revealed that during the initial outbreak, when London was attacked by the Infected, David was infected and attacked Selena, forcing her to kill him. Kirk then arrived and gave Selena his machete, which she now wields today.
After burying David's decomposed corpse, along with the necklace and earrings he gave her, Selena sets their old home on fire and has another flashback to before the outbreak. In this one, while David and Selena are making love, David confesses that should he die before Selena, he will not care if she falls in love with someone else after. Meanwhile, back in District 1, the Second Outbreak of the Rage Virus occurs, and civilians, including Clint, are herded into and locked in the safe rooms. When the Infected break into the safe room Clint is in and begin massacring and infecting the uninfected crowds, Clint escapes into the streets, and meets up with Charles and a wounded Janice. Janice is shot and killed by a sniper when Step Three of Code Red is executed, and Charles, heartbroken, allows the Infected to kill him while Clint escapes.
Selena returns to District 1 in time to save Clint from an Infected, and the two reunite. When District 1 is firebombed, the two survive by hiding in the Thames when the Air Cavalry arrives. They later escape into the ruins of London, and hold up in a deserted high-rise building while the US Army vents chemical gas into the streets. Once the gas has cleared, Clint and Selena escape down the Thames in a military motorboat, and travel in the boat across the English Channel to France. They stay in Paris for a couple of days, and Selena lets go of her machete so she can finally move on from everything she went through in Britain. Clint and Selena then leave on a plane for New York, and as the plane takes off, the Infection appears in Paris on the ground.
- Mark (flashback and illusion only)
- Jim (flashback only)
- Hannah (flashback only)
- Frank (flashback and illusion only)
- Clint Harris
- David (flashback and corpse only)
- Phillips (comic series)
- Dr. Klein
- Major Sanders
- Ahmed Karzaii
- Captain Stiles
- Dr. Billingsworth
- Kirk (flashback only)
- Lead Glaswegian Raider
- Sergeant Luis Rodriguez
- Private Jones (corpse only)
- Major Henry West (corpse only)
- Eliott Muniz
- Tammy Harris (cameo)
- Andy Harris (cameo)
- It was shown in 28 Weeks Later that the US-led NATO force responsible for repatriating London fully believed that the last Infected in mainland Britain died of starvation five weeks after the original outbreak; whereas the comics depicted that some of the Infected further north (particularly in Scotland) were still alive, and that the US military were aware that the Shetland Islands were recently infected (as they had quarantined the Islands). It was made apparent by Sergeant Rodriguez in Issue 18 that this was because the US Army believed (incorrectly) that the mainland was free of Infection.
- In a flashback of Mark's death in the first film at the start of the comics, Mark's hair is blonde.
- The design of Selena's machete changes between issues.
- In Issue 5, Eliott stated that the Rage Virus originated in London. However, it was shown in 28 Days Later: The Aftermath that the Rage pandemic started in Cambridge before spreading throughout Britain.
- In the comics, Clint and Selena were taken into District One days before the outbreak in the green zone. However, in 28 Weeks Later, Scarlet Levy stated that Alice Harris was the first survivor to be found and taken into the safe zone in over two months.
- When Raj confronts Clint and warns him that Dixon is coming to kill him and Selena, there is blood down his face (from the injury to his head Dixon caused earlier). But when Clint leaves the room, the blood on Raj's face is gone.
- There is an Easter Egg in Issue 24 of the comics; the boat which Clint and Selena use to escape from District One to France has "Nelson, Aragon, Woodard, 2011" on its side; this is a direct reference to writer Michael Alan Nelson, artist Alejandro Aragon, colour artist Nolan Woodard, and the year in which the issue was published (2011).
- Tammy and Andy Harris from 28 Weeks Later make a cameo in the comics when Selena sees them when they are travelling across London to their old home. Tammy, Andy and Alice are also mentioned several times (albeit not by name).
- Near the end of the final issue, an air hostess on Clint and Selena's plane mentions a non-commercial helicopter from Britain (most likely Flynn's helicopter) crashing after flying into France from Britain. When the plane takes off moments later, a horde of Infected are seen running through Paris on the ground. This would imply that Tammy, Flynn and Andy crashed in France at around the same time the Rage Virus surfaced in Paris. It would also imply that the Infection appeared there only a couple of days after District One was destroyed.