Plot: "Dirty Bomb" probes the realities and implications for public health policy of a disaster that many consider to be all but inevitable: a terrorist attack on a major city using a radioactive "dirty bomb. " The program strives to answer crucial questions about this menacing new weapon in the terrorists' arsenal, questions such as: What exactly is a dirty bomb? How dangerous could one be, and how much radiation could it release? What will need to be done to clean up after an explosion?