In Cold War Vienna, Milena (Russell), a young American woman in her twenties, is rushed to the emergency room after apparently overdosing. With her is Alex Linden (Garfunkel), an American psychiatrist who lives in the city as a teacher. Through fragmented flashbacks, the narrative depicts the story of their romance, which ultimately amounts to an unhealthy obsession on the part of Alex.
Through these developments, Milena is revealed to suffer from depression and is married to a much older man, Stefan (Elliott), whom she occasionally crosses the border to see during the course of her affair with Alex. Though Alex initially enjoys her free-spirited ways, he becomes embittered by her lifestyle, which includes impulsive promiscuity and heavy drinking. Through spying on Milena, Alex becomes emotionally strained, and eventually tries to control her – leading to horrifying results, due in large part to very bad timing.
Throughout, at the hospital where doctors and nurses fight to save Milena’s life, an investigator, Netusil (Keitel), comes to realise that there may be more to her case than a simple suicide attempt. When he discovers the truth, he tries to corner Alex into a confession.
Finally the film reveals that Alex raped her when she was unconscious. Later, just before Alex can confess, Stefan arrives and reveals that Milena has survived and is out of danger. Alex returns to America where, some time later, he sees Milena getting out of a taxi. He shouts to her but she ignores him.