When Elsa accidentally strikes Anna in the heart with her frozen power, the only way Anna can be saved from death is by an act of true love. Thinking she must be kissed by her handsome prince, Anna pleads for him to kiss her. But he refuses, and turns out (spoiler alert) to be evil, bent on taking over the kingdom. He charges her sister Elsa with treason for Anna's impending death.
Then Anna realizes Kristoff truly loves her. She sets off across a fjord to find him. At the same time, Hans chases Elsa onto the same fjord, intent on killing her. Anna reaches Kristoff, but sees Hans is about to kill Elsa. She throws herself between the two and freezes solid, blocking the blow. As Elsa grieves the loss of her sister, Anna begins to thaw. Her sacrifice for her sister constitutes an act of true love.
It surprised me how the handsome prince turned out to be evil, breaking a stereotype. The screenwriters thought of a great twist in making sisterly love the key to saving Anna and subsequently Elsa instead of the love of a man, as it usually is in Disney princess movies. Frozen is my favorite movie of 2014 so far.