Darkness at Noon, novel by Arthur Koestler, published in 1940. The action is set during Joseph Stalin’s purge trials of the 1930s and concerns Nicholas Rubashov, an old-guard Bolshevik who at first denies, then confesses to, crimes that he has not committed. Reflecting Koestler’s own disenchantment with communism, the plot examines the dilemma of an aging revolutionary who can no longer condone the excesses of a regime he helped establish. The book is a powerful examination of the moral danger inherent in a system that is willing to employ any means to an end.