In a winter landscape, men are cutting ice from a lake, singing as they work. A boy, Kristoff (voice: Jonathan Groff), is working alongside them (not very expertly) accompanied by his reindeer Sven (voice: also Jonathan Groff).In the Kingdom of Arendelle, the king and queen have two daughters: the elder, named Elsa (voice, young Elsa: Eva Bella; voice, Elsa: Idina Menzel), and the younger, named Anna (voice, young Anna: Livvy Stubenrauch; voice, Anna: Kristen Bell). Elsa was born with a power to create and manipulate snow and ice, but Arendelle is not a place where magic is valued.One night Anna wakes Elsa wanting to play. Elsa allows herself to be persuaded when Anna suggests building a snowman. Elsa turns the ballroom into a winter playground, complete with a snowman she calls Olaf. The girls play gleefully until Anna makes a leap Elsa wasn't prepared for and the blast of power meant to create a pile of snow hits Anna in the head, knocking her out and turning several strands of her hair white. The king and queen rush both girls to a group of trolls in the kingdom's mountains.The troll's leader, Pabbie (voice: Ciarán Hinds), says Anna can be saved. However, he advises the family that it might be best to not have Elsa use her powers around Anna, and manipulates Anna's memories so she has no knowledge of her sister's powers, remembering only the fun they've had. Pabbie also explains that Elsa's powers will grow, and can prove a danger if she cannot learn to control them.The girls' parents then separate the two, and having no memory of what has occurred, Anna is unable to comprehend why her sister is not allowed to play with her. She often comes to Elsa's closed door and tries to coax her out by asking, "Do you want to build a snowman?" As a further precaution, the sisters are also kept from leaving the castle.While Anna's life is dull but normal, Elsa's powers grow stronger as she matures. Her father cautions her to wear gloves to keep her icy magic in check, and to conceal her feelings, because strong emotions seem to cause her powers to manifest in unexpected ways.A few years later, the teen-aged princesses lose their parents to a storm at sea. Anna goes again to Elsa's door, pleading for consolation from her only remaining family member. But Elsa, though she sits sadly on the the other side of the door, refuses to communicate with Anna.Three years after the death of their parents, Elsa comes of age, and the castle prepares to crown her as the kingdom's queen. Elsa is nervous about emerging from her seclusion and receiving the many guests. When she gives the order to open the castle gates, Anna eagerly rushes out into the city. While falling into a boat, she meets a handsome prince, Hans of the Southern Isles (voice: Santino Fontana).Elsa remains nervous during the coronation ceremony. The bishop (voice: Robert Pine) has to remind her to remove her gloves before she takes up her golden orb and scepter. Holding them, she turns to face the congregation, but almost immediately she sees the gold is turning to ice. She returns the orb and scepter hurriedly to the bishop and puts her gloves back on.At the coronation ball, Anna and Elsa share their first words face-to-face in many years. At first things appear to be going well, and then Elsa is asked by the duke of Weselton (voice: Alan Tudyk) to dance. The duke is a buffoon, but an important trading partner. Elsa declines and has Anna go in her place.After dancing with the duke Anna takes the floor with Hans, who dances beautifully, and then they go off to talk. Hans tells how he is the youngest of 13 brothers, and as the two talk further, they seem to have much in common. Hans soon proposes to Anna, and she eagerly agrees.Returning to the ballroom, they ask Elsa to bless the marriage, but Elsa grows distraught and will not agree. She asks the guests to leave, setting Anna off on a tirade at her sister, who now not only seems distant emotionally, but also seems intent on keeping her from happiness.Unable to contain her emotions, Elsa makes a violent sweep with her arm, causing a barrier of sharp icicles to appear. Shocked at the room's reaction to her powers, Elsa rushes from the room, through the city, and across the waters of the fjord, where her feet cause ice to form. She flees far into the mountains, leaving winter in her wake.Anna calls after her sister, but as she, Hans, and the other guests watch, the waters of the fjords completely ice over, and the air takes on an icy chill.The Duke of Weselton fears that Elsa is an evil sorceress (it's starting to snow) and wants to hunt her down, but Anna proposes a solution: she will find her sister, and get her to stop the snow and ice. Leaving Hans in charge of the kingdom, she takes off on horseback as the snow intensifies.Meanwhile, Elsa has found her way to a high precipice on the kingdom's North Mountain. It is here she realizes that far away from what she was taught, being on her own, she can begin to control her powers! She constructs an elaborate ice palace, changes her confining wardrobe into a shimmering dress, and vows to stay in seclusion, where she feels she can be herself, and harm no one else.Anna's pursuit is hindered when her horse is spooked and rushes off. Noticing some smoke nearby, she finds a small trading post run by a man named Oaken (voice: Chris Williams). The trading post has very little winter gear (it's supposed to be the off season). As she is about to leave, a mountain man named Kristoff appears, wanting to buy supplies. (It's the ice-cutter boy, all grown up.) When the topic turns to the weather, Kristoff says the cold seems to be coming from the North Mountain. Kristoff and Oaken have an altercation over the drastic increase in the prices of the items Kristoff needs, and Oaken throws Kristoff out into the snow.Kristoff and his reindeer Sven take refuge in a barn on Oaken's property, but are soon met by Anna, who has bought Kristoff's supplies for him, on condition he take her up the North Mountain immediately.Kristoff eventually agrees, and the two head off into the night, Sven pulling the sled. As the discussion turns to Anna and her sister, Anna explains about her whirlwind engagement, which causes Kristoff to question the wisdom of getting engaged to someone she met that day. However, the sled is soon surrounded by wolves. They escape by leaping a chasm, but lose the sled. Kristoff is at first upset that his sled is gone, but is willing to help Anna keep going, worried for her safety. Anna promises she will replace the sled.After some wandering, the two encounter a beautiful frosted glen and a talking snowman named Olaf. Anna recognizes Olaf's design as being similar to one Elsa made when they were young. Anna and Kristoff tell how they want to find Elsa to bring back summer, and Olaf suddenly grows excited; it's his dream to see what summer is like. The two do not reveal what summer will mean for him, but follow him as he leads them to Elsa's ice palace.Meanwhile in the city, where Hans is providing shelter and help for Arendelle's people, Anna's horse returns, riderless. Hans asks for volunteers to join him in bringing Anna back. The Duke of Weselton volunteers his two bodyguards, and secretly tells them to take care of Elsa if they should encounter her.At the Ice Palace, Anna asks Elsa to reverse the artificial winter. Elsa is surprised to learn that her entire kingdom is frozen, and Anna is surprised in turn to learn that Elsa doesn't know how to stop it. But Anna insists her sister's powers are no reason why they should be so distant. However, Elsa flashes back to their childhood and grows scared, demanding Anna leave.Elsa retreats to the upper portion of the palace, and Anna follows her, pleading with her sister that they can solve this problem together. But Elsa grows so upset that she unleashes an icy chill, of which a portion strikes Anna in her heart.Realizing she has hurt her sister again, but desperate to be left alone so she won't be able to do it any more, Elsa creates an enormous ice creature, Marshmallow (voice: Paul Briggs). It chases Anna, Kristoff, and Olaf out of the palace. After their escape, Kristoff notices that Anna's hair has started to turn white. Fearful that she may be injured, Kristoff takes her to his family...who happen to be a group of rock trolls -- the same ones that saved Anna many years before. Kristoff explains that as he had no family at a young age, the trolls took him and Sven in.The trolls are overjoyed to meet Anna, and at first they eagerly believe that she is Kristoff's girlfriend. However, he tells them that she is injured and needs their assistance. Just as he did years before, Pabbie comes forward and examines Anna, but concludes that this time her sister's powers struck her in the heart. Pabbie cannot save her; Anna's heart has begun to freeze. Pabbie says "an act of true love can melt a frozen heart." Anna quickly tells Kristoff that Hans can surely help, and they take off for Arendelle.Meanwhile, Hans and his party have reached Elsa's palace. At first menaced by her snowman bodyguard Marshmallow, the duke's bodyguards charge into the palace and corner Elsa. As they attempt to kill her with crossbows, she begs them to leave her alone, but they continue to attack her. She threatens to kill them, trapping one with icicles and fending the other off before Hans intervenes. Then one of the bodyguards sends an icy chandelier crashing down, knocking her out.Elsa awakens in a prison cell in Arendelle, her hands chained and encased in steel mitts. As she looks out over the frozen kingdom, Hans appears, telling Elsa that Anna has not returned, and pleads with her to stop the winter. Elsa claims she can't, and must be let go to keep others from being harmed.Meanwhile, Kristoff and Sven arrive at the castle. Anna's condition has grown worse, a chill coursing through her, and more of her hair has turned white. Several of the castle staff escort her in; she looks back as Kristoff and Sven leave. Anna is brought to Hans and tells him that he has to kiss her in order to save her.The castle staff in the room quickly leave to give them privacy. Hans places Anna in a chair, leans in as if to kiss her... and says "if only there was someone here who loved you!" As Anna looks at him in shock, Hans explains that as the youngest of 13 brothers, he had no chance at claiming his family's throne, so he went looking for a royal family he could marry into. Unable to get to Elsa, he made Anna's acquaintance and played on her naivete. He intended to marry her before causing some form of "accident" for Elsa that would clear his path to the throne.However, given Anna's current condition, he plans to simply let her frozen heart overcome her, then kill Elsa, ending the eternal winter. Anna tries to stop Hans, but he extinguishes the fire in the nearby fireplace before locking her in the room. It is then that Anna collapses, her hair now completely white.Hans goes to speak with the duke of Weselton and several other dignitaries. He claims that Elsa has caused Anna to freeze to death, but before she died he and Anna recited their wedding vows. This apparently is enough to give him full authority to declare Elsa guilty of treason and sentence her to death.The palace guards go to Elsa's cell, but are detained when a wall of the cell collapses, and it is shown that Elsa has escaped into the cold.Meanwhile, far from Arendelle, Kristoff and Sven are trekking away when Sven urges Kristoff to go back. Kristoff claims he has no need to, but as they look back at Arendelle, a mysterious swirling cloud of snow begins to engulf the kingdom. The two then take off towards the growing danger.Olaf has managed to find Anna in the locked room, and seeing her freezing, quickly lights a fire in the fireplace. Anna explains that Hans wasn't her true love, and that Olaf should leave or he'll melt. However, the little snowman says he will not leave her side until he finds an act of true love that can save her. As they talk, Olaf recalls how Kristoff did so much to get her back to save her, when the wind blows a window open. Olaf goes to close it, but in the distance he sees Kristoff and Sven charging towards them.This gives Anna hope. She realizes that they're in love: maybe Kristoff can save her. Olaf helps her up, but in the hallway, ice springs up to block their path. Going out a window, the two slide down the castle's steep roofs. Anna attempts to make her way across the icy fjord, with Olaf close behind. However, as the wind picks up, Olaf is blown away, and Anna finds her hands beginning to turn to ice! Even so, she continues to move forward, calling out Kristoff's name.Meanwhile, Hans has found Elsa wandering the ice of the fjord. Thinking he's come for her, Elsa tells him to leave her alone, and take care of Anna. Hans lies and says that Anna was killed by Elsa's magic. The pain of this causes Elsa to collapse, the snow in the air suddenly hanging in stillness.The clearing of the whiteout enables Kristoff to see Anna, and he runs to her, but as Anna looks around, she sees Hans about to stab Elsa. Even with her own life at stake, Anna rushes in front of Hans, blocking the knife. As she does so, her frozen heart finally consumes her, turning her into a statue of ice, and shattering Hans' blade.Upon seeing Anna turned to ice, Elsa breaks down in tears, hugging her sister. No one is sure what to say, when Anna's icy form begins to change and gain color, and she returns to normal! Anna broke her own spell: saving Elsa was an act of true love.It is then that Elsa realizes what can end the winter: love. And with this realization, she dissipates the ice and snow, and summer returns to the kingdom. Olaf is found, and Elsa forms a small "flurry" above his head, which lets him survive the summer heat.In the aftermath, Hans is taken back to his kingdom by another of the royal guests, who promise to see he is punished for his crimes against the royal family of Arendelle. The duke of Weselton is as hotheaded as ever, and given his attitude, it is decreed that trade between Arendelle and Weselton shall be severed.Meanwhile, Anna makes good on her promise and replaces Kristoff's sled. She also makes him the castle's official ice deliverer. Kristoff is so grateful that he kisses her.Having come to grips with her powers and learning they can be a blessing and not a curse, Elsa uses them to create a wintry spectacle in the summer sky. She also turns the castle's courtyard into an ice rink, where she informs Anna that the gates to the castle will never be closed again. With the city's people in attendance, the sisters skate around the rink, happy that they are finally together again.