Maigret and his wife decide to take a short holiday with their family, but their stay is suddenly interrupted when Mrs. Maigret is taken ill with appendicitis. Returning from visiting his wife at the hospital, Maigret discovers a mysterious note that has been slipped into his coat pocket, alerting him to certain a patient at the hospital, Liliane Godreau, who subsequently dies. It also turns out that Liliane was the sister-in-law of the surgeon who operated on Maigret’s wife…