Tōru Kagami’s (Ren Osugi) subordinate Saito commits suicide in the middle of the Yuichi murder case investigation. At the suicide crime scene, Itomura finds a whistle in the close vicinity of the corpse. Before the suicide, Saita (Hatsunori Hasegawa) pays visit to Natsuko Etō (Maki Mizuno).
Itomura (Takaya Kamikawa ) believes that the murder case 18 years ago involved Natsuko’s brother and Saita was in charge of the murder case. However, he says that he was responsible for Natsuko’s brother’s death. Itomura asked Natsuko the nature of Saita’s business with her, but she repeatedly says, “Ask Toru.” As Itomura digs deeper into Saita’s case, Natsuko claims that she saw a silver spoon at the crime scene. What is the significance of the silver spoon? And what are Saita and Natsuko hiding from Itomura? The truth behind the 18 years old murder case remains convoluted and Itomura’s interest in the silver spoon grows stronger.
Itomura visits Saito’s mother, Saita Toyoko (Sasaki Sumie), and shows a picture of the crime scene to her. Toyoko claims that she knows nothing and the leads grow thinner. But the investigators discover that the whistle near Saito was a dog whistle. Oddly, on the dog whistle was a trace of iron oxide and particles of feldspar stone… Itomura’s detective work is put into test as he tries to find a the connection between Yoshiyuki Yamazaki’s untimely death, Saita’s “suicide,” and an 18-year old case that is in danger of remaining unsolved forever.