Irene Wagner (Bergman), the wife of prominent German scientist Professor Albert Wagner (Wieman), had been having an affair with Erich Baumann (Kreuger). She does not disclose this to her husband, hoping to preserve his innocence and their "perfect marriage". This fills her with anxiety and guilt. However, Johann Schultze (Mannhardt), Erich's jealous ex-girlfriend, learns about the affair and begins to blackmail Irene, turning Irene's psychological torture into a harsh reality. When Irene finds out that the extortion plot is truly an experiment in fear, she is driven into a homicidal/suicidal rage. But she is saved from suicide by her husband at the last minute, both sorry for what they did.