Seo Changbin, a talented K-pop idol and member of Stray Kids, discovers an old, forgotten track on his personal playlist. Intrigued by its haunting melody and mysterious lyrics, he learns that the song was written by a legendary, reclusive composer whose work was said to bring luck and success to anyone who performed it.

Curious, Changbin decides to incorporate the song into Stray Kids' upcoming album. As he and the group start working on the track, they experience a series of uncanny, almost magical events that seem to align perfectly with the song’s lyrics. However, these events also attract the attention of a shadowy figure who appears to be connected to the composer and has a hidden agenda.

As Changbin and the group delve deeper into the song's origins, they uncover a web of secrets that ties the song, the reclusive composer, and their own lives together. With the help of their friends and a few unexpected allies, they must unravel the mystery before their newfound fortune turns into a dangerous curse.