In The Dark Chain, George Valentine receives a heartfelt plea from Mrs. Purcell, a mother overwhelmed by the challenges of raising her son Buddy, a large young man with the mind of a child. She reveals that a cherished family heirloom, a delicate brooch, has gone missing from their home. Buddy, who is gentle and innocent, has developed a fascination with jewelry, leading Mrs. Purcell to fear that he might be involved in the disappearance. However, she firmly believes he would never steal anything, especially not from his own family.