Peter is a talented young composer who has so far not been able to get his revue “Traumschöne Nacht” in a music theatre. Behind the scenes of the “Alhambra”, a Paris music hall, he meets Violetta, a young up-and-coming artist. For her sake, Mr. Maroni, the director of the “Alhambra”, who is in love with Violetta but is rejected by her, has organized a costume party at which the young entertainer appears as a little flower seller. When Peter shows up there too, he believes that Violette is actually selling flowers.

Professor Charles Buisson, astronomer and Nobel Prize winner, has just discovered a nova. He informs the other observatories by telephone. Just as he thinks one of them is calling back, he finds himself on the line with a young woman threatening suicide at the Ruban Bleu cabaret, if her lover hasn't joined her by midnight. Intrigued, the professor decides to go and prevent the unfortunate woman from committing suicide. One of his students, who earns her living as an understudy in a knife act, helps him in his investigation, while the school principal and a policeman suspect him of being a prankster or even of selling drugs. For the scientist, it's an opportunity to discover a world of music-hall that he'd never known before: "I thought I knew the sky chart by heart, but there's one planet that was totally unknown to me: Earth. I'll be back!