Princess Ella of Merridale has magical powers that allow her to create ice and snow. She and her younger sister, Alli, often play winter games together---even in the summertime. 

One day at play time, Ella accidentally injures Alli by striking Alli's head with her magic. The King and Queen rush Alli to Merlin the wizard. Merlin heals Alli. 

Merlin then explains that Ella's powers are based on her emotions. He warns Ella that her powers are very strong and that  she must learn to control her powers or she might one day hurt Alli permanently, or even kill her.

The King and Queen separate the sisters in order to protect Alli from Ella’s unpredictable powers. Ella pretty much keeps herself locked in her room. Over the years, the sisters become estranged. 

Unfortunately, their parents died when the sisters were young adults, leaving Ella next in line for the crown. When Ella becomes 21, she has a birthday celebration and is to be crowned Queen of Merridale. 

Among the visitors arriving at the celebration is the handsome Prince Floki. Alli accidentally bumps into Floki, and they fall in love at first sight. During the coronation festivities, Floki  proposes to Alli and she accepts. 

When Alli and Floki ask for Ella’s blessing, Ella objects. She warns Alli that getting engaged so quickly is not a smart move. Alli thinks Ella knows nothing about life because she keeps herself locked away from everyone. The two begin to argue and Ella loses control of her emotions. Ella’s magic is exposed to everyone when everything around her starts turning into ice.

Ella doesn’t want to frighten the people so she runs away to the North Mountain. There, she finally accepts who she is and embraces her powers. She builds herself an ice palace to live in.

Alli goes out to find Ella so they can both find a way to put a stop to this eternal winter. She reaches Ella’s palace and  tells her that Merridale is in a state of eternal winter. Ella, however, doesn‘t know how to undo her magic. The two argue and Ella loses control again and accidentally strikes Alli too close to her heart with her powers. Alli know she’s in danger of dying, so she rushes off to find Merlin.

After Alli leaves, Floki shows up at the ice castle with his bodygaurds. Unbeknownst to Alli, Floki captures Ella and imprisons her back in Merridale.

When Alli finds Merlin, he warns her that she will literally freeze to death if the spell is not broken. He says that  breaking the spell requires "an act of true love." So Alli races back home so that Floki can give her a true love's kiss.

Arriving at Merridale, Alli finally reaches Floki. However, she is devastated when Floki refuses to kiss her. He turns away from her and laughs. He tells her that his intentions are to seize the throne and become King of Merridale. He leaves Alli locked in a room to freeze to death. 

Ella, however, uses her magic and is able to free herself from prison. She finds Alli and frees her too.

Floki discovers that the two sisters are missing and chases after them. When he catches up with them, he tries to kill Ella with his sword, but Alli blocks Floki’s sword with her arm just as she becomes solid ice. She saves Ella’s life.

The citizens of Merridale see Floki's treason, and they grab him and carry him to prison.