When four isolated elderly people die back-to-back at the same hospital by jumping out of the sixth-floor window, Su-Yeon doesn't understand why she's the only one at her precinct that seems to care. But her colleagues at the police force dismiss the case as a series of unfortunate suicides due to the patients' loneliness. But Su-Yeon doesn't have the privilege of looking away: her dearest friend, Grandma Eun-Shim, lives on the sixth floor, and Su-Yeon is terrified that something will happen to her next.

As Su-Yeon begins her investigation alone, she runs into a mysterious woman named Violette at the crime scene. Violette claims to be a vampire hunter, searching for her ex-lover, Lily, and is insistent that a vampire is behind the mysterious deaths. Su-Yeon is skeptical at first, but when a fifth victim jumps from the window, her investigation reveals the body was completely drained of blood. Desperate to discover the cause of the deaths, Su-Yeon considers Violette's explanation-that something supernatural is involved.