Adolf Verloc, a secret agent in the employ of the Embassy, has been embedded in the socialist Red Committee in London. He is summoned to the Embassy to meet with First Secretary Mr. Vladimir, who berates him for the lack of concrete results from his work; instead of just preventing attacks, Mr. Verloc is ordered to lead his radical associates to carry out a terrorist act that will strike at the very fabric of the British middle class, so that they will finally allow for repressive legislation.
Mr. Verloc—who lives with his wife Winnie, her mentally handicapped brother Stevie, and her mother in their shop selling shady wares—hosts Red Committee members Michaelis, Comrade Ossipon, and Karl Yundt. The radicals are quick to spout vainglorious statements, but Mr. Verloc despairs of their being able to accomplish the extraordinary act Mr. Vladimir has asked him to produce.
On a later date, Ossipon meets with the Professor, an eccentric, solitary man who produces explosives. Ossipon shows him a newspaper article about the Greenwich Bomb Outrage that had taken place in Greenwich Park that morning: a bomb meant for the Greenwich Royal Observatory detonated prematurely and blew the bomber to pieces without injuring anyone or causing any damage. The article says that Mr. Verloc was the killed bomber.
Leaving from their meeting, the Professor runs into Chief Inspector Heat, a police officer who has just investigated the scene of the bombing. After letting the Professor off, Heat meets with the Assistant Commissioner, his superior, and reveals his former acquaintance with Mr. Verloc. The Assistant Commissioner, annoyed by what Heat has been keeping from him, complains in turn to his own superior, Sir Ethelred, the Home Secretary, about the danger of using secret agents like Mr. Verloc. After his meeting, he walks to Mr. Verloc’s shop.
In the past few weeks, Mr. Verloc has spent some time in Europe; since coming back, he has been taking long walks with Stevie. Mrs. Verloc, who cares as a mother for her highly sensitive and easily devoted brother, is glad to see her husband seemingly taking care of the boy. However, on the day of the Bomb Outrage, Mr. Verloc, who has in fact not been killed, comes back home looking physically ill. After a visit from Mr. Vladimir and another from Chief Inspector Heat, Mrs. Verloc learns that Mr. Verloc had given Stevie a bomb for the Greenwich Observatory but that Stevie tripped and let the bomb off early.
At first, Mrs. Verloc is mute with shock, but then her years-long resentment towards her husband surges up, and she stabs him fatally. Terrified by the prospect of being hanged as a murder, she goes to commit suicide from a bridge. On her way, she runs into Ossipon and begs him to escape with her to the Continent. However, when Ossipon sees the dead Mr. Verloc at their home, he becomes terribly confused and frightened and ends up abandoning Mrs. Verloc on a train to the port. She later commits suicide on the passenger liner as it crosses the English Channel.
