During the 2022 celebration marking 30 years of diplomatic relations between South Korea and China, the president’s daughter Hana disappears with her bodyguard. Chief of Security Cha Jeong-hak is reminded of another disappearance connected to the 1992 summit that established diplomatic relations between the two countries.

Thirty years earlier, Jeong-hak and his friend Han Mu-young were assigned to protect a Chinese interpreter who attended a confidential meeting between the national leaders. Because she alone knew what had been discussed, intelligence authorities planned to eliminate her. Both men developed feelings for her, but she and Mu-young fell in love. A harmless incident on a sofa led Jeong-hak to misunderstand their relationship and request a transfer.

The interpreter created coded messages using musical notes, and she and Mu-young exchanged them through sheet music. When Mu-young learned that she was to be killed, he helped her escape from the Blue House. Pursued into the mountains, he sent her away alone and ignited a storehouse filled with pine pollen, dying in the explosion. Authorities branded him a spy, while Jeong-hak was tortured and removed from the security service.

In 2022, Hana has fled after classmates accused her of receiving favoritism in a violin competition. Lost in the same mountains with her bodyguard, she finds a glass bottle containing cloth marked with musical notes identical to those in an old score from the Blue House library. Her friend Suji, secretly Jeong-hak’s daughter, helps the security team locate them.

Hana and the others decode the message, revealing a final letter from Mu-young to the interpreter and Jeong-hak. Hana and Suji reconcile and perform music derived from the coded score at the anniversary ceremony.

The interpreter returns from China for the event. Jeong-hak gives her the recovered letter and the necklace she lost 30 years earlier, telling her that Mu-young is doing well. Mu-young’s spirit watches them and smiles. (2026 Version)