"The Lost Door" is about Kristina (Mikaela Fisher). She is a suspect in a murder inquiry. She is commited to a psychiatric hospital where she is being interrogated by a young female psychiatrist named Catherine (Anna Bielska). It's Catherine's goal to find out what goes on in Kristina's mind and whether she has commited the murder.
Kristina tells Catherine about her obsession for/addiction to her dancestudent Nicole (Nicole Auberger). Kristina has done everything in her power to be with Nicole. This has lead to dangerous and unforseen situations. First the film focuses on Kristina's story. But in the end, the film is also about the confrontation between the two women, Kristina and Catherine. Kristina manages to let Catherine open up to her own sexual repressed desires.