It's 2008 and the Reaper virus has spread throughout Scotland, resulting in the country being walled off by the British government. A Scottish woman brings her young daughter, who has an injured eye, to soldiers for rescue. The mother convinces the soldier to airlift her daughter to safety. She then hands the girl a letter. Years later and it seems the contained population is dying out. Another decade later and the virus reappears; this time in London. Prime Minister John Hatcher (Alexander Siddig
) and his puppeteer, Michael Canaris (David O'Hara
), share news with domestic security cheif, Captain Bill Nelson (Bob Hoskins
), of survivours in Scotland, believing there to be a cure. They ask him to send in a team into the walled-off area to find medical researcher, Dr. Kane (Malcolm McDowell
), who was last known to be working on a cure in Scotland. Nelson chooses Eden Sinclair (Rhona Mitra
), who was the little girl from the beginning of the movie. She has had her lost eye replaced with a cybernetic one and leads the team.
To the north of the wall, whilst investigating Kane's location, Sinclair's team are ambushed by plague survivours. Some of the team are killed, Sinclair and Dr. Talbot (Sean Pertwee
) are captured whilst Sergeant Norton (Adrian Lester
) and Dr. Stirling (Darren Morfitt
) escape. Sinclair is left in a cell and subjected to torture by the leader of the survivours, Sol (Craig Conway
) and his 'assistant', Viper (Lee-Anne Liebenberg
). Dr. Talbot is barbecued alive before the entire survivour population and then eaten. During this ritual, Sinclair escapes from her cell and comes across Kane's daughter, Cally (MyAnna Buring
) who is also imprisoned. Freed by Sinclair, Cally takes her to a nearby waiting train which is being manned by her friend Joshua, (Martin Compston
). Norton and Stirling meet up with them as the train begins moving also being chased by Sol and the survivours. The train takes them to the mountains where they take a shortcut through a hidden military facility to the castle where Kane dwells. The team are surrounded by Kane's medieval soldiers. Joshua is killed and everyone else surrender to the soldiers. Sinclair is told by Kane that the survivours are naturally immune to the virus and that Sol is his son who he has been warring with. She also discovers that there is no cure for the virus. Sinclair defeats Kane's executioner, Telamon (Henie Bosman
), and escapes the castle with help from the team. They retreat to the facility where they find a Bentley in storage. They decide to use it in an escape but Norton is killed in the process.
In London, political leaders plan to cut off the 'hot spots' where the virus is spreading. Canaris convinces Hatcher to let the infected population dwindle before sharing any cure Sinclair's team may bring back so the population is easier to control. Although the government leaders are isolated, an infected man infiltrates the building and infects Hatcher. Knowing he has the virus, Hatcher commits suicide and Canaris takes over his position as Prime Minister.
In Scotland, Sinclair, Cally and Stirling run into Sol's men on the highway and lead them into a car chase. Sol attempts to hijack the Bentley, but while he is on the roof, Sinclair plows the car through a roadblocked bus, decapitating him. Using a GPS cell phone also taken from the facility, Sinclair summons a government gunship and hands over the cure to Canaris: the immune survivor Cally from whose blood a vaccine can be replicated. Canaris, who arrives with the gunship, shares his plan with Sinclair to withhold the cure for political reasons and invites her back to London. Sinclair chooses to stay and goes to find her old home located at the address on the envelope her mother had left her. Nelson, having been given the envelope by Sinclair before she left on the mission, finds her there. Sinclair provides Nelson a video of her conversation with Canaris, which she recorded with her cybernetic eye. Nelson takes the recording back to London and airs it publicly, exposing Canaris' plan to hold back the cure. Sinclair returns to the location where she and her team were first attacked by the cannibalistic tribe and, presenting them with Sol's severed head, is cheered as their new leader.