Helena (Hel) Brant visits her estranged twin sister Siri at a luxurious alpine sanatorium, Himmelstal. Much to Hel’s horror, she soon realizes the sanctuary is an escape-proof psychiatric hospital and Siri has swapped places with her, leaving her trapped.

Panicked Hel tries to tell authorities - founder Dr Fisher and Dr Kowalska - about Siri’s betrayal. When Hel finally succeeds in getting them to check confirm her story by looking at her fingerprints, she is horrified to discover they ‘prove’ she is Siri.

Hel learns about a secret escape organization between inmates and is determined to use them to help get her out of Himmelstal. By doing so, she inherits some dangerous enemies… and several possible lovers.

Hel desperately tries to persuade staff that she is not a psychopath, but no one believes her claims. Dr Kowalska discovers Dr Fisher’s true unsettling mission behind the sanctuary.

Hel learns more about Siri’s disturbing and violent past. Hel’s fate is in the hands of a dangerous psychopathic inmate, Carol, who rules the valley.

Siri sends Hel an upsetting message from the outside. Hel continues concocting her escape plan. Carol arranges a meeting with the Head of Security and accuses Hel of an unspeakable crime.

A shocked Hel learns that her sister has reportedly died in a car crash. A fellow inmate tells Hel that she a psychiatrist embedded as a patient, and that she believes her story. They decide to talk to Fisher, her long-time friend and colleague.

Hel’s fellow inmate is brutally tasered by Fisher when she confronts him. Another doctor discovers Hel is telling the truth, but is driven off the road and killed by another member of staff. As her options are rapidly running out, and Hel has nothing to lose, she decides to accept a ‘kamikaze’ plan to escape. But nothing ever seems to go to plan in Himmelstal…