A nurse caring for two patients in an affluent household becomes embroiled in a violent mystery after a dinner guest falls ill and a subsequent tragedy. Suspicions and rival testimonies ripple through family and visitors as a pragmatic detective pieces together clues, red herrings, and small physical tokens—a black-edged card, a counterfeit note, and ultimately a gunshot—that reveal hidden motives and tangled relationships. The plot advances through interviews, narrow escapes, and confrontations, gradually exposing domestic secrets and the chain of events that led to crime.