The narrative subversion of Frozen hinges upon a careful manipulation of classic fairy tale conventions. Throughout the journey, the prophecy stated by Grand Pabbie—that "only an act of true love can thaw a frozen heart"—leads both characters and audiences to expect a classic "true love’s kiss". When Elsa accidentally strikes Anna in the heart during their confrontation at the ice palace, Anna slowly turns to solid ice.
Believing Prince Hans is her true love, Anna is rushed back to Arendelle, only for Hans to extinguish the room's fireplace, lock her inside to freeze, and reveal his plan: as the thirteenth son of a minor kingdom, he used Anna to usurp the crown and plans to execute Elsa for treason.
In the blinding blizzard on the frozen fjord, Anna spots Kristoff running toward her, realizing he truly loves her. At that moment, she hears Hans drawing his sword behind Elsa to execute the grieving queen. Instead of saving herself with Kristoff’s kiss, Anna makes the deliberate choice to turn away, throwing herself between Hans's blade and Elsa. At the exact instant Hans’s blade strikes, Anna freezes into solid ice, shattering the sword and stopping the murder.
Elsa collapses in grief, weeping over her frozen sister. Anna's voluntary sacrifice is the act of true love; because Anna performed it selflessly, her frozen heart thaws, restoring her to life. This revelation teaches Elsa that love, not fear, is the key to mastering her power, allowing her to thaw the kingdom and reclaim her throne.