The Adlers decided to spend a week in their old apartment in the City of Paris, once again enjoying their life as before. Irene was overjoyed when Sherlock and Lupin followed there, and the three herdsmen immediately investigated the mystery of the disappearance of Arsène's cousin, a nobleman who had many dreams. In an effort to find a trace to find the man back, they walked through a slum in Paris, even falling into a deadly fight between two bandit gangs. Now it's Irene's turn to try to prevent another war from erupting... And as a consequence, he and his family suffered a great loss that was unspeakable....