Psychology of the Criminal

The lodger, Mr. Sleuth, is portrayed as a religious fanatic who reads the Bible and Cruden's Concordance, uses red ink, and performs 'experiments,' suggesting a disturbed mind that rationalizes murder as divine vengeance, exploring the intersection of madness, religion, and violence.

The museum exhibits and the analysis of the Avenger as a 'cunning, quiet' madman delve into the criminal mind and methods.

Mr. Sleuth's odd behavior, his urgent need to conduct experiments at night, and his discomfort when discovered hint at a disturbed psychology.

Mr. Sleuth's Bible quotations about death and madness, his cold hands, and his hand-rubbing gesture reveal a disturbed mind, linking to criminal psychology.

The lodger is revealed as a 'religious maniac' and 'homicidal maniac,' highlighting the psychological underpinnings of the Avenger murders.