In 1920s Dublin the Irish Civil War has just come to a close. Gypo Nolan, a strong, brutish, and dull-witted ex-policeman, and his childhood friend Frankie McPhillip, are both members of a revolutionary organization—until Gypo betrays Frankie by informing on him to the police to collect a reward. Frankie is promptly killed in a shootout, and Gypo soon finds himself the subject of an investigation and manhunt as the revolutionary organization mobilizes its soldiers and the working class to uncover the traitor and bring him to justice.

O’Flaherty was a Marxist and a member of both the Industrial Workers of the World and the U.S. Communist Party, and the novel’s foundation in the struggles of the working class and revolutionary politics reflect this background. It’s also rich in religious symbolism, with Gypo portrayed as a Judas to the revolution.

The Informer was a critical and commercial success, launching O’Flaherty’s literary career. It went on to be adapted into a 1935 film of the same name that won four Academy awards.