Once upon a time, large, beautiful seaside hotels adorned the coast of Øresund – from Bellevue Strandhotel in the south to Hornbæk Badehotel in the north. While the film's director, Stig Lommer, was director of the Hornbæk revues, he was a frequent guest at the bars in these hotels. He loved the glamorous life in this setting and asked Arvid Müller to write a light-hearted "Sommer-Lommer-Spøg" (Summer Joke) about the "deeds of the night" at a seaside hotel. The now defunct Beaulieu (north of Taarbæk) and Marienlyst (in Helsingør) form the backdrop for bandleader Hans Herbert and his pursuit of summer guest Mrs. Winter. This drives the exchange broker to a spontaneous suicide attempt in the middle of a mannequin show. However, he is saved by Mrs. Holgersen, who believes it is for her sake, so she blossoms completely. So much so that she is completely unrecognizable to the manufacturer when he arrives at the hotel.

Der var engang, da store smukke badehoteller prydede Øresunds kyst. - Fra Bellevue Strandhotel i syd til Hornbæk Badehotel i nord. Mens filmens instruktør, Stig Lommer, var direktør for Hornbækrevyerne, var han en flittig gæst i baren i disse hoteller. Han elskede det mondæne liv i dette regi, og bad Arvid Müller skrive en lystluppen "Sommer-Lommer-Spøg" om "nattens gerninger" på et badehotel. Det hedengangne Beaulieu (nord for Taarbæk) og Marienlyst (i Helsingør) danner rammen om kapelmester Hans Herbert (Svend Asmussen) og hans jagt på sommergæsten, fru vekselerer Winter (Lily Broberg). Dette driver vekseleren (Kjeld Petersen) til et -spontant- selvmordsforsøg midt i en mannequinopvisning. Han reddes dog af fru fabrikant Holgersen (Bodil Steen), der tror, det er for hendes skyld, så hun blomstrer helt op. - Så meget, at hun er helt ukendelig for fabrikanten (Ulrik Neumann), da han ankommer til hotellet.