It is a nice, sunny morning outside the Palaffi Bank. The beautiful strains of Anna Zador's voice are floating down the street. She brings a small bouquet from her country garden to place on Count Willie Palaffi's desk.
On the stroke of eight, the Count arrives at his office, after a night out with two or three girls. In his office, he passes Anna without even a sideways glance. Family friend and vice-president of the bank, Whiskers, rebukes Willie for the decadant, wasteful life he leads, but Willie just orders gifts for the girls waiting outside. Contemplating the future of the bank if its president continues on in this fashion, Whiskers decides that the Count must marry. Seeing Anna at her desk, Whiskers invites her to the Count's birthday party that night, thinking that she would be a perfect wife for Willie.
That night, at the birthday party at the Count's house, guests arrive in expensive fancy dress (costumes). Anna arrives in a simple angel costume and enters as the guests make fun of her. Whiskers maintains that she is a nice, wholesome girl and tells Willie's friends to be quiet and give her a chance. Count Palaffi greets her and goes back to his friends. Whiskers intercedes and tells Willie to dance with Anna. After only a few minutes, the Count makes an excuse to go to his room, where he immediately falls asleep.
While he is asleep, Willie dreams that an angel, Brigitta (who looks just like Anna), comes in his window. He immediately realizes that she's the perfect girl for him. After she convinces him that she is there to marry him, they leave through the window and get married. Their honeymoon is spent in a fancy hotel. They go out shopping together and meet many of Willie's friends, including Baron Szigethy, the Palaffi Bank's chief depositor. Brigitta's first Dinner Party is a disaster, as she is too straightforward with all of Willie's society guests. Since she is so much trouble to him, she decides to leave him. The Count then travels all around searching for his angel, but he cannot find her.
Count Palaffi awakens to find that it has all been a dream and only a few minutes long. He rushes downstairs to a lonely Anna, to tell her of his love for her, "his angel". They stand, hand in hand, as everyone joins in a last chorus.