The Queen's Bang tiara, the centerpiece of the Robanov imperial treasures exhibit, is stolen by Kaito Kid! The exhibition hall is suddenly enveloped in white smoke, and by the time it has cleared, the tiara inside the case has vanished. Because a gas mask would ruin his disguise, it's unlikely Kaito Kid was wearing one. The suspects are narrowed down to Amuro, Azusa, and Kazami, who were standing near the tiara without masks, so Conan decides to investigate.