A Mad Idea: A series of stupid coincidences causes the young Munich painter Paul to convert his uncle's castle into a hotel for four weeks. But he can't complain: business is good and he has plenty of guests. For exmple, there's Theo Muller with his revue troupe. For reasons of "sound", Muller calls himself "Miller", which, of course, causes more confusion. His daughter, the beautiful Evelyn, is confused with Mabel Miller, who has come to the hotel on a mission for her filthy rich father ... namely, to estimate the worth of the castle.