Screenwriter Takashiro Sasaki (Haruko Kato) murders her younger sister Kazuko (Moeko Ezawa) whom she had a long-standing feud, and makes it look like a robbery gone wrong. Furuhata suspects his favorite screenwriter, but they wouldn't have been able to throw away the weapon. To prove her guilt, Furuhata enlists Imaizumi as Sasaki's newest assistant.
脚本家・佐々木高代（加藤治子）は、長年不仲だった妹・和子（絵沢萌子）を殺害し、強盗の犯行に見せかける。古畑は高代を疑うが、彼女の犯行ならば凶器を遠くに捨てる余裕は無かったはず。しかし、どこをいくら探しても凶器が見つからない。
