Let me just say upfront this is a tough story to do, and we'll probably be criticized for hyping a threat that many people feel is improbable, if not impossible.
However, if the FBI is worried and the Russian government is worried, then I'm worried.
As far as we know, Osama bin Laden and al Qaeda have never gotten their hands on a nuclear weapon, but that's not for lack of trying. In 1998, bin Laden said acquiring nukes "for the defense of Muslims is a religious duty." And we know al Qaeda tried on at least one occasion to buy nuclear material from a bogus dealer who was more interested in stealing the terrorists' money.
Now, the FBI has called together security officials from 28 countries to discuss the nuclear threat and to map strategies for sharing information and cutting off the supply of materials on the black market.
Tonight on the CBS Evening News with Katie Couric we'll talk one-on-one with FBI chief Robert Mueller, who warns in stark terms that the destruction of 9/11 could pale in comparison that caused by a nuclear strike against an American city.
We'll also take you inside the New York Police Department to show you what cops and technology are doing on the home front -- the last lines of defense.
While we don't want to exaggerate the threat, we can't ignore it either. The 9/11 Commission called the government's missteps leading up to 9/11 "a failure of imagination". Taking that lesson, no conceivable threat should be off the table for security officials or out of bounds for public discussion.