Cillian Murphy stars a Jim, an ordinary bicycle courier who lives in London. After animal rights activists break into a secure animal research facility in order to free some chimps, an extremely dangerous virus which the lab has been researching is released into the general population. This virus is transmitted in the smallest drop of blood even getting infected blood in a wound or in the mouth is enough to transmit the infection. Within seconds, the infected victim is in a permanent state of uncontrollable rage and expressing that anger as violence directed at everyone around him. Twenty-eight days after the virus is first released, Jim awakens in a deserted hospital. It seems he was in a coma caused by a car hitting his bike, and while he was unconscious the virus was spreading.
Leaving the hospital, Jim finds himself confused and alone in a desolate London, where he starts looking for any signs of life scattered newspapers seem to make no sense, writing as they do of 'quarantine' and 'evacuation'. Entering a church, an infected priest attacks him, and he gets his first indication of what he might be up against. He is rescued by Selena (Naomie Harris), one of a small number of people who have not yet been infected and are fighting to survive. They team up with Frank (Brendan Gleeson) and his daughter Hannah (Megan Burns) and set off seeking other survivors and safety, but they have no idea that the virus is not the only danger they will face.
This is a fine creepy British shock horror picture with bags of atmosphere and palpable threat. The zombie-like victims of the virus are not the mindless shuffling idiots of Romero's films, but strong, fast and capable. The film looks fabulous most notably, the shots of a deserted and devastated London are particularly poignant. The plot is both gripping and thoughtful it doesn't just focus on the threat posed by the virus, but considers the bigger picture also. One wonders, however, why Jim wakes up naked in the hospital it seems National Health Service financial cutbacks may have extended as far as hospital gowns!