Daisy calls Donald to accompany her to a costume party and waltz championship. Donald trusts his own dancing abilities, but Huey, Dewey, and Louie tell him that he can't dance the waltz, only the Charleston. They help him practice the waltz for hours until Donald can't stop dancing, and writes a letter to Daisy to meet him at the bus stop at 7:30, signed "the waltz king". Due to his dance moves, the handwriting doesn't look like his, but the nephews know Daisy will guess the letter is from Donald, and leave it at her home.
Donald sleeps to rest from the practice, and when the nephews awake him, he gets amnesia and forgets everything after Daisy calls him, even his waltz moves. A sad Donald goes to Daisy's home to explain tings to her and finds the letter. Given his amnesia and the different handwriting, Donald believes "the waltz king" is a rival for Daisy's love.
Donald waits for "the waltz king" at the bus stop at 7:20 and attacks three different men who go to the costume party, and Donald thinks they may be "the waltz king". After that, three disguised ladies arrive awaiting their boyfriends, and when they find Donald almost killed them, they ruin his clothes in retaliation.
Daisy calls Huey, Dewey, and Louie, and they explain to her that Donald left a letter and was going to be at the bus stop. Daisy goes there and finds a battered Donald, whose memory is slowly coming back, listening to the Blue Danube in his head. Daisy thinks his clothes are good for a vagrant disguise and carries him to the costume party.
The Nephews, believing Donald is still amnesiac, steal the waltz partitures and exchange them for boogie woogie. Daisy thinks they dance the boogie very well, but Donald reveals he cannot dance the boogie now, only Blue Danube. Daisy angrily pursues Donald while Huey and Dewey wonder what went wrong, and Louie gets amnesia.