Daisy calls Donald to accompany her to a costume party and waltz championship. Donald trusts his own dancing abilities, but Huey, Dewey and Louie signal him that he doesnt, dance waltz but charleston. They help him practicing waltz for hours until Donald can't stop dancing, and writtes a letter to Daisy to await him in the bus stop at 7:30, signed "the waltz king". Due to his dancing moves, the handwriting doesn't seem 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 anything after Daisy called him, even his waltz moves. A sad Donald goes to Daisy's home to explain her and finds the letter. Given his amnesia and the different handwriting, Donald believes "the waltz king" is a rivalñ for Daisy's love.
Donald awaits "the waltz king" in the bus stop at 7:20 and attacks three different men who go to the costume party and Donald thinks may have been "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 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 and listens the Blue Danube in his head. Daisy considers 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 change them for boogie woogie. Daisy is convinced they dance the boogie very well, but Donald reveals he cannot dance boogie now, only Blue Danube. Daisy angrily pursues Donald while Huey and Dewey wonder what went wrong, and Louie gets amnesia.