Many Americans consider the idea of a nuclear bomb exploding in an American city to be Hollywood science fiction, but FBI warnings that terrorists may be planning an attack on Chicago are hitting close to home and are eerily familiar. One month after the Sept. 11, 2001, attack on the World Trade Center, a CIA agent code-named "Dragonfire" reported that Al Qaeda had acquired a small nuclear bomb from the former Soviet arsenal and had brought it to New York City. Vice President Dick Cheney and hundreds of other government officials evacuated Washington for a then-undisclosed location. President Bush dispatched...