captions paid for by nbc-universal television good evening. this is no longer the story of rampant flooding in a faraway place halfway around the world. tonight, it's the story of a natural disaster so large, so staggering it threatens to destabilize the entire nation of pakistan -- a country with nuclear weapons in a dangerous part of the world. tonight, water covers about a fifth of pakistan, the length of the country from north to south, an area roughly equal in size to the state of florida. the rainwaters have been relentless this monsoon season and more of them are on the way....