Conductor Seong-jin leads an orchestra in which his fiancée, Soo-yeon, plays the cello. Their harmonious life takes a sudden turn when Soo-yeon vanishes, leaving behind nothing but a cryptic video message.

Overwhelmed by grief, Seong-jin struggles to move on but finds himself inexplicably captivated by Mi-joo, the cellist chosen to fill Soo-yeon's place. One stormy evening, swept up in their mutual longing, Seong-jin and Mi-joo cross a line they cannot undo, succumbing to temptation within the walls of Soo-yeon's home.