Helena goes to visit her twin sister Siri at a luxury sanatorium located in the Italian Alps. The tension between them quickly escalates as she refuses her relative's rather unusual request. Siri wants Helena to pretend to be her for a few days. The next day, Helena discovers that her sister has disappeared, and the clinic is far from a paradise. But escaping from there is not the most important task. First and foremost, she must survive. After all, every patient and their doctors pose a hidden threat.