As the science museum is about to open, the precious Seven Luminaries Bronze Plate mysteriously disappears in the sealed constant-humidity room. Through polarized verification, humidity records, and sound trajectories, everyone deduces step by step that the bronze plate was not stolen, but rather slipped into the display stand's interlayer due to residual cotton threads pulling the counterweight. After the truth comes to light, the responsible person honestly admits the mistake and rectifies it in time, the cultural relic safely returns to its place, and the exhibition reopens. The story reveals that facing mistakes honestly, speaking with evidence, and having the courage to take responsibility are the best protection for cultural relics and the public.