"Diamond Pin" by Carolyn Wells delves into the darkly comedic world of eccentric New York widow Ursula Pell, who revels in playing cruel pranks on her unsuspecting guests, particularly her niece and nephew, the heirs to her vast fortune. When Ursula is found brutally murdered in a locked room following a dinner party, suspicion falls on her niece Iris, the latest target of Ursula's humiliating jokes, while all evidence seems to implicate her nephew. As renowned detective Fleming Stone steps in to unravel the mystery, listeners are treated to a tale of family rivalry, hidden treasures, and the search for truth.