Set in London in 1886, the novel follows the life of Adolf Verloc, a secret agent. Verloc is also a businessman who owns a shop which sells pornographic material, contraceptives and bric-a-brac. He lives with his wife Winnie, his mother-in-law, and his brother-in-law, Stevie. Stevie has a mental disability, possibly autism, which causes him to be excitable; his sister, Verloc's wife, attends to him, treating him more as a son than as a brother. Verloc's friends are a group of anarchists of which Comrade Ossipon, Michaelis, and "The Professor" are the most prominent. Although largely ineffectual as terrorists, their actions are known to the police. The group produces anarchist literature in the form of pamphlets entitled F.P., an acronym for The Future of the Proletariat.

Writing near the peak of the British Empire, Conrad drew, among other things, on his native Poland's national experiences and on his own experiences in the French and British merchant navies, to create short stories and novels that reflect aspects of a European-dominated world--including imperialism and colonialism--and that profoundly explore the human psyche.