Vivian Gordon went out before midnight in a velvet dress and mink coat. Her body turned up the next morning in a desolate Bronx park, a dirty clothesline wrapped around her neck. At her stylish Manhattan apartment, detectives discovered notebooks full of names--businessmen, socialites, gangsters. And something else: a letter from an anti-corruption commission established by Governor Franklin Delano Roosevelt. Led by the imperious Judge Samuel Seabury,...