A king without a son invites eligible royals and other high aristocrats for his eldest daughter princess Sophie's 18th birthday party, expecting her to get engaged with a suitable one, such as interested prince Friedrich. She also receives her late mother's most prized legate, a golden ball allegedly magically inspiring wise decisions, but loses it playing by the castle park lake. While a man lurks around, a talking frog promises to retrieve the ball if she takes him in as her companion. He keeps the deal, Sophie runs off leaving only a pearl string she first offered, but when the frog comes demand his prize at the royal dinner, and proves himself a talented singer, the king orders her to keep her promise, clearly unwillingly. Only when he exhausts her patience and is smashed against her bedroom wall, his evil fairy spell is broken and he re-assumes the shape of neighboring Brabant's heir, prince Floris. Now she falls in love and dumps Frederic to the king's horror, but must wait anxiously if he will return.
—KGF Vissers