Mr Verloc appears to be a simple shopkeeper in London who lives with his wife’s family at the back of his shop. But in reality he also works as a spy for a foreign government and has links with a group of anarchists who meet regularly at his shop. When a bomb goes off in Greenwich Park, everyone presumes it was meant to blow up the Royal Observatory nearby, as an act of terrorism. Can the police discover who was responsible for the explosion and why it didn’t reach its target?