Witness, by Whittaker Chambers, is the story of Communist penetration of the United States government by an underground cell, run by Whittaker Chambers. His underground espionage apparatus includes Alger Hiss, an assistant to the Assistant Secretary of State; Harry Dexter White, an assistant to the Secretary of the Treasury; Julian Wadleigh in the Trade Agreements section at State; and Vincent Reno at the Aberdeen Proving Grounds, then a secret military installation. These people pass government documents to Chambers, who has them photographed and passed on to Colonel Bykov. He, in turn, passes them on to Moscow.

Chambers becomes a Communist when he is in college at Columbia College in New York. He has been to Germany, which is still suffering the devastation of World War I, and feels certain that there will be a World War II. The world is in a crisis and, like many students and intellectuals, the question is what can be done about it. He finds the answers in Communism. During the Purge, he begins to question his own actions and beliefs, and decides to break with Communism in 1938. He hopes to get Hiss and others to break with Communism as well. Chambers remains in hiding for a year and then takes a job at Time. The Communist smear campaign against him begins, as this is a usual Communist tactic against ex-Communists. A friend convinces Chambers to become an informer and sets up an appointment with the Assistant Secretary of State for Security. Nothing comes of the meeting.

Eventually Chambers is called to testify at the House Un-American Activities Committee hearings, where he identifies Alger Hiss as a Communist. Hiss denies ever having met Whittaker Chambers. Eventually Nixon and the other HUAC members bring Chambers into the hearings room, and Hiss acknowledges that he knew him by another name. Hiss eventually sues Chambers for libel. At the pre-trial hearing, Hiss's lawyers ask for any documents Chambers has. Chambers produces documents that connect Alger Hiss to Soviet espionage. There are federal grand juries, HUAC sub-committees and the lawsuit all happening at the same time. The HUAC sub-committee subpoenas any other evidence that Chambers might have, and finds he takes three rolls of microfilm out of a pumpkin in his pumpkin patch where he had hidden them. These are the famous 'pumpkin papers'. They are the documents that linked Hiss, and others, to Soviet espionage.

The later chapters of the book contain excerpts from the hearing transcripts, so the reader can read exactly what happened and how. Chambers brings the reader into the mind of the Communists and what drove them as they worked for the government that they swore allegiance to and betrayed. The reader also learns how the Soviet apparatus operated and what its deserters were afraid of, given the mentality of the participants. Even though the book is long, it is worth the time spent reading it. It provides insight into the events in the Communist scare era.