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