The last naturally occurring case of smallpox was diagnosed in Ali Maow Maalin, a hospital cook in the picturesque seaport of Merca, Somalia, on 26 October 1977. But in August 1978, the smallpox virus crept like a thief in the night from a laboratory in Birmingham to re-inhabit human flesh and blood. What happened next has all the hallmarks of a Greek drama or Shakespearean tragedy, with the shocking but mysterious appearance of a dreaded disease...