Introducing Detective Jim Barnett the Third.Countess Isabelle de Maunbassant, an old acquaintance of Lupin, has invited him to catch the murderer of her husband Philippe, offering him her husband's emerald ring as a reward. She invited the three suspects to her chateau in order to set a trap for the culprit: gem collector Frederick Autorett, the count's nephew Allan Dubois and failed businessman Pierre Schmidt. However, in the midst of her announcement, a blackout hits the chateau and the Countess is fatally shot...