In the mid 1960s, the American actress Joan Copeland was finding it increasingly difficult to secure parts. One day, though, she was up for a major television role and met with the writer, producer and sponsor. They were enthusiastic. Rehearsals were planned.

Then she was asked if she was related to the playwright Arthur Miller. She confessed that he was her brother. She never heard from them again. Copeland was not alone. Other actors, directors and producers found themselves blacklisted, alongside others from Broadway and Hollywood, who had been members of the communist party in the 1930s and 1940s, or espoused radical causes.

Meanwhile, people were summoned before the House Un-American Activities Committee (HUAC) or its Senate equivalent. The latter was chaired by a junior senator from Wisconsin, Joseph McCarthy. There, they were required to confess to their “sins” and to name others who had been party members.

During the second world war, the Soviet Union had been an ally to the United States. After the war, however, it was seen as the enemy. In August 1949, four years after Hiroshima, the then USSR exploded an atom bomb at a remote test site in Kazakhstan.

A year later, McCarthy claimed to have a list of 205...