Ji-na, an ordinary hotel employee whose life seems peaceful, is suddenly thrust into a dark mystery when her older sister, Ji-hyun, mysteriously disappears. Returning to the sprawling, scheduled-for-demolition Rose Mansion apartment complex to find her, Ji-na encounters a web of suspicious neighbors who all harbor dark secrets, strange fetishes, and malicious intentions. As she digs deeper alongside a tenacious detective named Min-soo, Ji-na realizes that the residents of the apartment building know far more about her sister's disappearance than they are letting on. Set against the claustrophobic and decaying backdrop of an old residential complex, the series blends mystery, thriller elements, and social satire. Every neighbor she meets—from the seemingly helpful apartment representative to the creepy security guard and aggressive residents—appears to have a motive. The psychological tension escalates as long-buried secrets, greed, and trauma come to light, transforming the search for a missing person into a desperate fight for survival.