Three years after his sister’s tragic death in the notorious "Barcode Murder Case," rookie officer Choi Moo-Gak is still haunted by her death. The trauma left him numb, stripping him of his ability to feel pain, taste, or smell. Driven by revenge, Moo-Gak joins the police force, determined to catch the elusive serial killer. Meanwhile, Oh Cho-Rim, the sole witness and survivor of the same murder, has lost all memory of the incident. Instead, she develops an unusual ability: the power to physically see scents as colorful trails in the air. When fate brings Cho-Rim and Moo-Gak together, her supernatural gift and his relentless pursuit of justice make them an unlikely but formidable team. As they grow closer and dig deeper into the case, they uncover a chilling truth that connects them more than they ever imagined.