This dramatic dance was performed at the end of the movie after John 'Lucky' Garnett (Astaire) finds out Penelope 'Penny' Carroll (Rogers) is engaged to Ricardo 'Ricky' Romero (played by Georges Metaxa).
As she is walking up the stairs, he begins his serenade to her in hopes that she will understand how heartbroken he is over losing her.
At first, the dance is slow and somber, but eventually the pace and tempo pick up, and Lucky and Penny seem to be together again.
However, in the final movement, Penny twirls out of the room and doesn't come back, leaving Lucky standing there forlorn.
Fred Astaire recorded the song commercially (Brunswick 7718) and it proved popular.