In the aftermath of the 9/11 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 postal system caused chaos and fear. But there was a far greater danger that had government security advisers around the world even more alarmed: smallpox.

In his terrifying account of what happened, and what could still happen, Richard Preston reveals the true horror faced by victims of smallpox, raises serious 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.