"He remembered a book by Koestler"

Arthur Koestler (1905-1983) wrote Darkness at Noon after becoming disillusioned with, and leaving, the Communist Party of Germany in 1938.  Published in 1940, the book brought him instant fame, with its devastatingly critical portrayal of Communism.  The main character Rubashov is arrested, imprisoned under harsh conditions, tried and executed in an unnamed country ruled by a dictatorship, but there was little doubt the novel referred to the Soviet Union.  It served to draw attention to the harsh realities of life under Stalin's regime.