Taken by famous photographer Martha Holmes, the following photo shows Danny Kaye, June Havoc, Humphrey Bogart and Lauren Bacall reacting to a hearing of the House Un-American Activities Committee in 1947.
The committee was created to investigate the communist ties of American citizens. In 1947 it held 9 days worth of hearings to investigate the ties Hollywood had with communism and whether they were producing communist propaganda. As a result, numerous artists were blacklisted by the movie industry. Bogart took part in a movement against the committee, protesting its limitation of free speech.
Interesting fact: The committee was created in 1938, but was only abolished in 1975.
Interesting fact, part II: Holmes is better known for her iconic photographs of Jackson Pollack.