In the aftermath of the September 11th attacks in the USA, the Western world had to deal with a new threat: bioterrorism. In October 2001 a series of anthrax attacks through the American postal system casued chaos and fear. But there was a far greater danger that had government security advisers around the world even more alarmed: smallpox. In this account of what happened and could still happen, Richard Preston reveals the horror faced by victims of smallpox, raises questions about what happened to the smallpox viruses that were kept in storage after the disease was eradicated in 1979, and shows just how easy it would be to create new strains of smallpox that would be able to overcome any vaccination, leaving the population defenceless.