Written for a general readership, this narrative recounts events surrounding the 1993 outbreak of a killer virus in the southwestern United States, explains how the Sin Nombre hantavirus was identified, and discusses what has happened since then with regard to that virus. Interspersed is more general information about hantaviruses around the world and an overview of what is known (and not known) about viruses and how to stop them. Some color distribution maps and photos enhance the text. Appendixes include details of how to avoid the virus (getting rid of mice), and books and websites for further information.