A beautiful young woman appears at the threshold of Commissioner Brunetti’s office. The commissioner recognizes her at once: she is Immacolato’s sister—a nun who looked after his mother in a nursing home. But to Brunetti’s surprise, when the woman introduces herself, she gives a completely different name—Maria Testa. It turns out she left her monastic order after a string of deaths in the hospital, which she considers suspicious. The commissioner decides to check whether Maria’s fears are well-founded—or whether she is deliberately exaggerating everything to justify her escape from the harsh monastic life.