Dr. Harleen Quinzel, a psychiatrist at Gotham's infamous Arkham Asylum, finds herself drawn to a mysterious new patient who has been locked up following the high-profile murders of Thomas and Martha Wayne. The man, known only as "John Doe," stands out among the criminals and lunatics she's used to treating. Her curiosity piqued, Harleen becomes increasingly fascinated by his enigmatic and broken personality. As their sessions progress, she is determined to unravel the madness that consumes him. What starts as a professional obligation slowly evolves into an obsession as Harleen delves deeper into his mind, unaware of the dangerous transformation brewing beneath the surface.