To cover the ICU medical bills for her niece Lily, 27-year-old Chloe takes a job at a federal prison notorious for its brutality. Soft-natured and naively kind, she finds herself in a life-or-death situation involving sexual assault in Episode 1 after breaking protocol to open a cell door out of sympathy for a violent inmate who was feigning illness. She is saved at the critical moment by Kael—a death-row inmate held in a top-secret underwater dungeon fifty meters below ground—whose act of snapping the attacker's neck with his bare hands leaves Chloe deeply traumatized. While Kael appears to be a vicious criminal awaiting execution, he is actually the ultimate godfather controlling the global underground arms trade and the BDSM underworld; he voluntarily entered the prison to turn it into his personal playground and has long harbored a morbid, possessive obsession with Chloe’s innocence and fragility. During the pump room incident in Episode 11, Kael breaks free from inescapable heavy-duty shackles to reach Chloe, crushes her emergency alarm, and—using Lily’s medical coverage as leverage—officially initiates a volatile, forced-romance dynamic with her.
