30 - One of My Sons by Anna Katharine Green

When a young girl desperately calls upon a passing gentleman, Arthur Outhwaite, for aid, he finds himself embroiled in a mystery he never anticipated. He becomes the last person to see her grandfather alive, tasked with delivering a letter to a person whose identity remains unknown. As he navigates a home filled with strangers, Outhwaite must unravel the enigmatic circumstances surrounding the old mans death. Join him in this gripping tale of intrigue and suspense.