A murder takes place. Hong Yi Young, who is a timpanist, does not remember what happened on the day of the murder. She is simple-minded and suffers from insomnia. Hong Yi Young looks for a job. She happens to meet Jang Yoon. He is bad at singing but is a pianist in an orchestra. To help with Hong Yi Young's insomnia, Jang Yoon calls her every night. They try to find the truth about the murder. Meanwhile, Nam Joo Wan is an orchestra conductor. He has charisma and showmanship. Ha Eun Joo is a violinist in the orchestra. She is arrogant.