Anna Katharine Green 
Initials Only 

The mystery book "Initials Only" by Anna Katharine Green was released in 1911. The main focus of the narrative is the inquiry into the apparent connection between the passing of a rich businessman and a mysterious gang identified only by their initials. In order to learn the truth about the murder and the secret society, Mr. Gryce, the primary investigator, must negotiate a labyrinth of lies and deception. Several suspects emerge as the inquiry progresses, each with their own goals and secrets they wish to keep hidden. Mr. Gryce solves the case by making wise deductions and meticulous observations, exposing the identity of the killer and the actual motivations of the secret organization.