London is under threat. It has become a haven for political exiles and anarchists. Frequent bomb threats and disturbances interrupt the lives of the city's inhabitants, who live in fear of the terrorists in their midst. One such terrorist is Verloc. He is the secret agent who is given the mission to strike right at the heart of London's pride by blowing up Greenwich Observatory. But his decision to drag his innocent family into the plot leads to tragic consequences on a more personal than political level.