In 2008, an unknown killer virus, known as the "Reaper Virus", has infected the country of Scotland. Unable to contain the outbreak or cure the infected, the British government builds a massive 30-foot wall that isolated Scotland from the rest of Great Britain. Whilst the quarantine was deemed a success, the extreme method employed by the government destroys diplomatic and economic relations between the UK and the rest of the world. Now a pariah state, the UK collapses into a dystopia, rife with unemployment, civil unrest and extreme economic turmoil.
Twenty seven years after the start of the quarantine, a group of armed police officers discover several people in London infected with Reaper Virus during a routine investigation. Prime Minister John Hatcher shares satellite footage of survivors in Scotland with domestic security chief Captain Nelson. Believing a cure may exist, Hatcher orders Nelson to send a team into Scotland to find medical researcher Dr. Kane, who was working on a cure when Scotland was quarantined. Nelson chooses his top police officer, Major Eden Sinclair, to lead the team. Sinclair is originally from Scotland, having escaped as the quarantine began at the cost of her right eye. For Sinclair the mission is also personal, as she hopes to learn if her mother survived or not.
Sinclair's team crosses the wall to Glasgow, Dr. Kane's last known location. In Glasgow, while searching the local hospital for survivors, Sinclair and her team are ambushed by a group of marauders. Sgt. Norton and Dr. Stirling manage to escape, while the team suffers heavy casualties. Sinclair and Dr. Talbot are captured by what turns out to be a huge gang of brutal cannibals, led by the power-hungry Sol, who plans to use her as leverage to cross the wall, allowing his army to start their invasion on England, which will bring Great Britain into the Golden Age. He then leaves for the sacrificial ceremony to join the rest of his gang, who burn Dr. Talbot alive before devouring his body. With the help of Cally, another prisoner, Sinclair escapes and kills Viper, Sol's second-in-command. She meets with Norton and Stirling, and the three escape on a train. Cally reveals that she and Sol are Kane's children. Unsatisfied with Kane's rule, Sol abolishes martial law by creating his own army.
Meanwhile, back in London, everyone present ends up infected with emotional outbursts related to the Reaper Virus, destroying everything in sight in an ongoing riot. Hatcher plans secretly to isolate the central London area because of the infection when an infected man breaks into Hatcher's office and tries to kill him. Nelson shoots and kills the infected man, but his blood splatters on Hatcher. Hatcher is quarantined by his right-hand man, Michael Canaris, who also takes his place as de facto prime minister. Hatcher later commits suicide, unable to take much more of his successor's scam.
After leaving the train, Sinclair's group is arrested by soldiers armed with archaic weapons and armour. They are taken to a medieval castle and imprisoned. Their leader, Marcus Kane, tells Sinclair the truth: there is no cure, only people with a natural immunity. Originally a medical researcher, he was devastated when his family was left behind during the quarantine. After losing his wife, Kane became a twisted, sadistic lord who now hides from the world around him. Angry to see Sinclair return to Scotland after the start of the quarantine, Kane sentences her and her group to death, pitting Sinclair against Telamon, his executioner, in a small fighting ground to entertain his followers. During the duel, Sinclair subdues and kills Telamon while the rest of the group escapes, retrieving their equipment and rescuing Sinclair.
Sinclair, Norton, Stirling and Cally escape to a fallout shelter entrance on horseback. They locate an underground facility in the forest and find an intact 2007 Bentley Continental GT, which they fuel up. Kane's medieval knights arrive and kill Norton. Sinclair and the others drive the Bentley back to the quarantine wall. On the way, they are intercepted by Sol's gang, which seeks to avenge Viper once and for all. After a high-speed chase, Sol and many of his men are killed and Sinclair's group escape.
Using a phone retrieved from the fallout shelter, Sinclair calls Canaris, who later arrives in a government gunship. Canaris then tricks Sinclair into trading Cally - after Stirling suggests that her blood can be used to create a vaccine to treat the virus - revealing his scheme to let the Reaper Virus spread all over the UK, as both a form of population control, and for shady profit. It's the only way to preserve his role as creator of the Reaper Virus.
Cally and Stirling board the gunship with Canaris while Sinclair returns to her old house in search of her mother, followed by Nelson, who flew into the quarantine zone to speak with his superior officer. While Sinclair confirms that her mother has perished due to the virus, she is able to retrieve a picture of her. Sinclair gives Nelson a recording of Canaris' coup d'état scheme. The recording is later broadcast to the rest of the country, much to Canaris' dismay, as it spells doom to his career. Sinclair retrieves Sol's head and returns to his gang; she throws the head onto the ground, announcing to the marauders, “If you're hungry, try a piece of your friend”. The marauders stand in shock for a moment before bursting into cheering, accepting Sinclair as their new leader.
Rhona Mitra as Major Eden Sinclair
Bob Hoskins as Bill Nelson,
Malcolm McDowell as Marcus Kane,
Alexander Siddig as Prime Minister John Hatcher.
David O'Hara as Michael Canaris,
Craig Conway as Sol,
Lee-Anne Liebenberg as Viper,
Hennie Bosman as Telamon (The Gladiator)
Also cast as part of Eden Sinclair's team were Adrian Lester as Sergeant Norton, Chris Robson as Miller, and Leslie Simpson as Carpenter. Sean Pertwee and Darren Morfitt portrayed the team's medical scientists, Dr Talbot and Dr Stirling, respectively. MyAnna Buring portrayed Kane's daughter Cally. Emma Cleasby played Eden's mother