How did Mark Felt, the anonymous Watergate source that Woodward and Bernstein called Deep Throat, escape detection by the F.B.I.? As this Nation article explains, Mark Felt was "in charge of finding the source of Woodward and Bernstein's Watergate scoops. In a twist worthy of le Carré, Deep Throat was assigned the mission of unearthing--and stopping--Deep Throat."