A basement in Frankfurt is shared by two petty criminals, Horst and Walter. They recruit Rosemarie, a pretty but penniless blonde, to be the bait for their day job as street musicians.
When she enters the lobby of a smart hotel, hoping to pick up a businessman, she is kicked out by the concierge. She does however catch the eye of a group of businessmen who meet in the hotel and one of them, the married Hartog, sets her up in an apartment.
While Hartog is away at an exclusive equestrian event, Rosemarie picks up Fribert, a wealthy Frenchman who, to the horror of Hartog and his family, brings the uninvited Rosemarie to the event. Hartog gives Rosemarie a cash pay-off, which she immediately splurges on a convertible.
Fribert takes her over, not for sex but to improve her image by ditching her cheap clothes and décor. His plan, when he unveils it, is to use her for industrial espionage. He wires her apartment, after which she has to get businessmen into her bed and get them talking.