White House Season on Discovery continues with "The President's Gatekeepers", revealing the extraordinary behind the scenes history of the White House Chiefs of Staff. Called the world's second toughest job - and also the world's worst, the White House chiefs of staff translate the presidents' policies into reality - or disaster. They are the inside eyewitnesses to history, and the confidants with whom the president, and the first lady, share their secrets. Spanning nine administrations, "The President's Gatekeepers" reveals which White House Chief of Staff Dick Cheney blamed for bringing on his first heart attack? And why was Rahm Emanuel so apprehensive about taking the job? Also, which 25-year-old Chief of Staff was put in charge of reviewing J. Edgar Hoover's infamous FBI files before forwarding them to the President? In this two part special "The President's Gatekeepers" provides a compelling look at the world of the closest confidante the President has.