Op een avond in mei.

Peter Gruber, a young tenor from Vienna, gives piano lessons to Daisy, the daughter of a dentist. They fall in love and when Gruber has to perform in Antwerp, Daisy follows him there. She pretends to be an American musician and manages to get a job with Gruber's orchestra. Daisy's worried father sets off in pursuit of his daughter, accompanied by a certain miss Lola.