In February 1895, London woke up to a loud bang. A large pillar of smoke showed that a bomb had exploded in the Houses of Parliament. Security forces were activated immediately and they arrested a suspicious young laborer near the area.

Mycroft Holmes, at the service of the crown, was commissioned to investigate the relationship of the young laborer with anarchist groups. He thinks it will be an easy task that he can do from the comfort of his armchair in the Diogenes Club — until he is informed of disturbing news; his younger brother Sherlock Holmes, Consulting Detective, has been hired by the boy’s parents to prove the innocence of his son, who believes to be a scapegoat of a dark conspiracy.

For the first time, the brightest minds in London face each other. Was the young laborer involved in this terrible attack or he is just a scapegoat for a dark conspiracy?