A princess loses her golden ball in a deep pond. A frog agrees to help her get it out, provided she let him be with her, to eat at her table and sleep on her pillow. She promises, but upon getting the ball, forgets her promise and runs off to the castle. The frog follows her and eventually gets to the castle, where the king makes her keep her promise.
The frog eats off her plate, and drinks out of her goblet, and they retire to her bedroom where he demands to be put on her pillow. Instead, she picks him up and throws him against the wall, where he turns into a handsome prince. (In some variations, she has to kiss him.)
The prince explains how he was changed into a frog by a wicked witch and doomed to remain in that form until a princess released him. They fall in love and are married. On the wedding day, a splendid carriage arrives, driven by the prince's faithful steward, Hans. Hans had been so unhappy when his master was changed into a frog that he put three iron bands around his heart to prevent it from bursting with sorrow. During the drive the iron bands crack open because Hans is so happy to see his master restored to his former shape and travelling to his kingdom with a beautiful bride. The prince and princess never forget the faithful Hans, who loved his master so well.