Kaoruko finds evidence that Isshiki has been living at Takahashi's house, and then Sakon discovers that the telephone handsets in the museum had been tampered with. Sakon tricks Isshiki into revealing that he knew about the telephone tampering, discrediting his alibi and exposing him as the murderer. It appears that Museum's director Yuuki Mari realized that the Egyptian knife that Isshiki purchased was a fake. Isshiki then killed her to hide his grave professional mistake.