In order to promote the sale of beer and wine, the German government has outlawed all soft drinks. As a result, soft drink speakeasies have been born, the most successful being the Club 21. Here, customers can sample owner Golo's vintage ginger ale and cream soda while being entertained by his girlfriend Gitta. It doesn't take long for Police Commissioner Bauer to get wind of these unsavory dealings, however, and as Golo leads his patrons in a rousing song of patriotism, the Commissioner leads his officers in a typically inept raid.

That evening, Dresden's elite gather at the Bauer mansion to celebrate the Commissioner's birthday while his daughter, Ilse, urges him to put aside his troubles. A vengeful Golo is on his way to sabotage the party when he is struck by a car and knocked unconscious. Brought inside the Bauer home, he awakens not as Golo, but as Michael Bramleigh, a well-to-do gentleman of utmost sophistication. Just one problem - he has no recollection of the past six months of his life. Ilse proves a sympathetic listener and a smitten Michael soon proposes marriage. Before consenting to the wedding, Commissioner Bauer calls upon a team of psychoanalysts to diagnose the bridegroom's affliction. After some libidinous babbling, they make one sound suggestion, 'Watch Your Head'. Michael skips away whistling, confident of a secure future with Ilse. Then a birdhouse falls on him.

Transformed into Golo once more, with no memory of the previous month, he returns to the Club 21 where he renews his relationship with Gitta. Learning that the Commissioner's daughter is to be married, he plots to kidnap the bride and hold her for ransom. The following day, zealous guests anticipate the wedding ceremony as a nervous Bauer barks out orders to his troops. While Gitta and the gang create a diversion, Golo locates Ilse, who, thinking he is Michael, begs him to elope with her. Happy to have such a willing hostage, he steals her away to his conveniently stashed motorboat and speeds off to an inn at Schandau.

The next morning, Bauer laments his daughter's disappearance as irate wedding guests return and dismantle his house. Michael shows up - apparently he got hit on the head during intermission - and apologizes for missing the wedding. He and Bauer compare notes and deduce that Ilse must have been kidnapped by a dead ringer for Michael. The would-be groom sets out on his sweetheart's trail, only to meet up with Gitta, who, mistaking him for Golo, reveals Ilse's whereabouts. Michael rushes off to the Club 21 followed by the Commissioner, who finds himself side-tracked by Gitta.

Michael receives a warm welcome at the club - everyone thinks he is Golo. In an effort to infiltrate the gang, he decides to play along, but his plans are foiled when Golo's sidekick Katz becomes suspicious and takes him hostage. As Michael struggles for freedom, Bauer and his police arrive to lend assistance. During the ensuing brawl, Michael receives yet another blow to the head (this time from an overzealous Commissioner), at which point all gather anxiously to see who he'll be when he awakens. The result proves unsatisfactory to Ilse, who takes matters into her own hands.