The Broken Window Murder Case begins with Mr. Keen, a renowned investigator, being approached by Laura Franklin, whose father, John Franklin, has been brutally murdered in their home. The scene is set in a large estate, where Laura describes the chilling discovery of her father's body, stabbed to death in the library. Despite his reputation as a generous and well-liked man, Laura is perplexed as to why anyone would want to harm him. She explains that the police have no suspects, and the only clue is the broken window through which the killer entered.