T. B. Smith, Assistant Commissioner of Police, suspects that the murder of two foreigners is connected to Montague Fallock, a notorious blackmailer of prominent British citizens. Suspicion points to a wealthy businessman, who subsequently disappears, leaving a suicide note and a vast fortune to his ward, Doris. The investigation leads to a small country village and a secret house built by a wealthy hermit who is not what he seems. Who is the blackmailer and who is the victim?

Published in 1919, The Secret House explores the good and the evil that exist in human nature.