Budapest in the 1930s. Restaurant owner Laszlo hires pianist András to play in his restaurant. Both men fall in love with the beautiful waitress Ilona who inspires András to his only composition. His song of Gloomy Sunday is, at first, loved and then feared, for its melancholic melody sets off a chain of suicides. The fragile balance of the erotic ménage à trois is sent off kilter when the German Hans falls in love with Ilona as well.
