Insane

During a routine daytime walk in downtown, Soo-Ah is forcibly taken to a psychiatric hospital run by Director Jang Hyung-sik. The staff refuse to explain why she was taken and she is locked up and immediately subjected to coercive control and medications. She begins to realize she has little control over her fate.

Inside the hospital, Soo-Ah endures injections and 'medication' that numb her and suppress her protests. Any resistance triggers threats or violence from the staff, establishing a regime of fear. She hides her fear behind a mask of compliance.

While appearing to accept her fate, Soo-Ah secretly documents the hospital's abuses in a detailed journal. The act of writing becomes her lifeline and a potential evidentiary record against the institution. Her entries record repeated acts of cruelty and neglect.

A botched escape attempt exposes the dangers of attempting to flee. In response, the hospital subjects Soo-Ah to horrific punishment as a warning to others. The torture marks the cruelty of the facility and deepens her resolve to survive.

An orderly named Dong-sik, outraged by the facility's inhumane treatments, reaches out to Soo-Ah's boyfriend Woo-Jin to mount a rescue. The plan signals a glimmer of hope amid the oppressive regime.

A rescue attempt goes awry and the trio is captured. Woo-Jin is subjected to disembowelment, a brutal consequence of trying to break out. The hospital's grip tightens as the escape ends in failure.

Mi-ro, another patient, accidentally sets Hyung-sik's office on fire, triggering chaos. Hyung-sik races to recover a hidden safe containing illicit money, while Mi-ro helps the trio escape; Dong-sik stays behind to rescue the others.

Soo-Ah and Woo-Jin manage to escape the facility, but Hyung-sik drags Woo-Jin back inside and both are consumed by flames. The violent escape leaves Soo-Ah free but emotionally scarred by the loss.

Soo-Ah returns home to find her abusive step-father dead from a gunshot wound. Soon after, she is arrested on suspicions of murder and arson connected to the hospital fire. The trauma of the events now trails her into the legal system.

One year later, Nam-Soo, a programmer and former broadcaster, is assigned to uncover what happened to the burned-down hospital. He finds a notebook belonging to Soo-Ah and sets out to locate her and uncover the truth. The investigation reframes Soo-Ah’s case as a wider conspiracy.

Nam-Soo and his crew visit the charred hospital and unexpectedly encounter a heavily burned Dong-sik, who holds crucial memories about Soo-Ah's diary. This meeting propels the inquiry into deeper corruption.

Further digging reveals that the hospital was a front for an organ-trafficking ring and disappearances operation. Police Commissioner Kang Byung-joo, Soo-Ah's stepfather, and Jang Hyung-sik are connected as founder and protégé. The legal loophole that allows hospital admission with consent from two of three family members is exposed.

Nam-Soo broadcasts the findings and provokes Soo-Ah to reveal her own role and connections. Soo-Ah finally confesses her ordeals and her ties to Byung-joo, and Nam-Soo presents incriminating documents that implicate the hospital's mastermind. Public outrage grows as the truth comes to light.

With the hospital's destruction and the public pressure, Kang Byung-joo is believed to have committed suicide to avoid a life sentence. Soo-Ah is vindicated in court as the conspiracy is laid bare.

In the final reveal, Soo-Ah explains the true family connections: the diary belonged to Dong-sik, Woo-Jin was Soo-Ah's father, and Hyung-sik had killed Soo-Ah's mother. Soo-Ah admits she took revenge by killing Byung-joo, with Nam-Soo deciding to bury the secrets so she could live a normal life.