The story centers around Adolph Verloc, owner of a Soho bookshop and ostensibly a member of a group of home-grown anarchists, but actually in the pay of a foreign government. Verloc's quiescent wife, Winnie, maintains their stable household in which she tries to provide for her retarded brother and her aging mother under the thinly disguised irritability of her husband. The anarchist collective consists of "Doctor" Ossipan, who lives off his romantic attachments to women barely able to take care of themselves; "The Professor", an explosives expert who is so insecure that he is perpetually wired with a detonator in case he is threatened by police capture; and Michaelis, a corpulent writer composing an autobiography after a mitigated sentence in prison.

When Verloc is summoned to the embassy in whose pay he works, he receives a cold reception from his new superior, Vladimir. Vladimir tells Verloc that he's going to have to start producing or he'll lose the wages he receives. A humiliated Verloc is shocked when he receives orders to blow up Greenwich Observatory. As the scheme takes shape, it is Verloc who is compelled to execute the plan. But his doubts and fears are only too well justified, and despite his misgivings, he pushes ahead. However, it is the man-child Stevie who brings the enterprise to its ignominious end.