"Shin Se Kyung, were you the person who stole So Eun's composition?" Zoella asked. "What are you talking about!? I wouldn't do such a stupid thing," Shin Se Kyung replied. Have you ever met someone who is very talented in music? Who is beautiful and dedicated? Who has a keen observer and a talented musician for a best friend?Meet So Eun, who studies at Korean Music Art High School and joins a music competition with the help of her best friend, Zoella. The problem? So Eun's contest piece gets stolen. Now the two best friends need to find out who the culprit is. In the process, the two will discover something unbelievable. Only a person with a key to the music room could have done it, but who could it be? Wanna know? Let's find out and enter the world of mystery.