A murder takes place. Hong Yi-Young (Kim Se-Jeong), 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 (Yeon Woo-Jin). 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 (Song Jae-Rim) is an orchestra conductor. He has charisma and showmanship. Ha Eun-Joo (Park Ji-Yeon) is a violinist in the orchestra. She is arrogant.