Answer
Whittaker Chambers, a former communist turned government witness, testified that Alger Hiss, a high-ranking State Department official, had been a covert communist while working for the federal government. Chambers presented evidence of Hiss's involvement with the Communist Party, including secret documents that Hiss had allegedly given to him. Hiss denied the charges and the case became a landmark in the history of anti-communist investigations in the United States.