Tinkers' Nook is bustling with activity, for the tinker fairies are making snowflake baskets for the fairies of winter. A flock of snowy owls soon arrive for the baskets, bringing a final shipment order for Fairy Mary (Jane Horrocks) with them. Tinker Bell (Mae Whitman) watches as the birds headed off toward the Winter Woods in awe and curiosity.
Later that day, Tinker Bell volunteers to help Fawn (Angela Bartys) take animals to the Winter Woods to hibernate, but Fawn warns Tinker Bell that they could only bring animals to the border, and they aren't allowed to go into the Winter Woods. With Fawn distracted by a sleeping marmot, Tinker Bell jumps across the border into the Winter Woods. Tink gazes in wonder at the beautiful wintry landscape, enchanted by the delicate snowflakes falling around her, and the strange colors her wings create. The moment ends when Fawn yanks Tinker Bell back into the Autumn Woods. Touching Tink's wings, Fawn gasps at their cold temperature and rushes her off to the fairy hospital. A healing-talent fairy (Jodi Benson) examines Tink's wings and warms them to normal temperature. Tink remains curious about the sparkles and colors her wings made in the Winter Woods.
Tink flies off to the Book Nook, where she finds a wing-shaped book titled Wingology, but unfortunately, the page on "Sparkling Wings" has been chewed through. A reading fairy (Thomas Lennon) tells Tink that the author of the book, the Keeper, might be able to help her, but he lives in the Winter Woods. Preparing herself for the Winter Woods, Tink sneaks into the tinkers' workshop and climbs inside one of the snowflake baskets, and flies her way into the Winter Woods. Suddenly, the owl accidentally drops the basket, and Tink crashes into the snow. Realizing her book had been flung from her bag after the landing, she tries to get it back before another fairy finds it. However, Lord Milori (Timothy Dalton), the Lord of Winter, takes the book from Sled (Matt Lanter). Lord Milori asks Sled to return the book to the Keeper. Tinker Bell follows Sled to the Hall of Winter, upon arriving spotting the Keeper, Dewey (Jeff Bennett). Then another winter fairy rushes into the room and proclaims that her wings are sparkling. Simultaneously, Tinker Bell's wings begin to glow and sparkle, too. A force pulls her toward the frost fairy, whose name is Periwinkle (Lucy Hale). The girls ask Dewey to explain what was happening to their wings. Bringing Tink and Periwinkle to the giant snowflake, and positioning their wings, the whole chamber becomes filled with images of the mainland, baby's first laugh (shown to be Wendy Darling in the main movie), that split in half: one [Tinker Bell] to the Pixie Dust Tree, and the other [Periwinkle] to the Winter Woods. Tink and Periwinkle realize that they are fraternal twin sisters.
Suddenly, Lord Milori arrives, concerned over Tinker Bell's wing book, warning Dewey to send any 'warm' fairy back to the Autumn Woods. Dewey tells the girls they can have a little time to visit before Tink has to return home. The two go to Periwinkle's house, where she shows Tink her various items she had collected. Next, they go to the Frost Forest, to introduce Tink to Periwinkle's friends Gliss (Grey DeLisle) and Spike (Debby Ryan). They continue to spend time together the entire day. That night outside Periwinkle's house, as Tinker Bell builds a fire to stay warm, she realizes that if she can make it warm in the Winter Woods, she can make it cooler at her home. Suddenly, the snow floor melts beneath them, weakened by the fire. After the incident, Dewey tells the girls that Tinker Bell has to go home. The girls realize that they might never see each other again, but Tinker Bell comes up with a plan. When the three fairies reach the border, Tinker Bell begins to fake crying while whispering to Periwinkle to meet her at the border tomorrow. When Tinker Bell arrives home, she asks her friends Clank (Jeff Bennett) and Bobble (Rob Paulsen) for help. Hard at work, some of Tink's other friends stop by and learn of Tinker Bell's twin sister, excited at the prospect of meeting her.
The next day, Tinker Bell arrives at the border with Bobble and Clank, pulling along a snow-maker. Now able to keep Periwinkle cold enough, Peri crosses the border to the 'warm' side of Pixie Hollow. She meets Tinker Bell's friends, Fawn, Iridessa (Raven-Symoné), Rosetta (Megan Hilty), Silvermist (Lucy Liu), and Vidia (Pamela Adlon) and continues her tour of the warm side of Pixie Hollow, until Tink noticed Periwinkle's wings wilting. The snow-maker was running out of ice, and there wasn't enough snow to keep Peri cold, so Tink and Periwinkle return to the border. Lord Milori appears and instructs Periwinkle how to fix her wings. Queen Clarion (Anjelica Huston), arrives too, and sadly explains to the girls that they can never see each other again. As the girls go their separate ways, the snow-maker gets knocked into the stream, and creates a snowstorm.
Later that day, Queen Clarion tried to make Tinker Bell understand why the rule about not crossing the border was so important, as so did Lord Milori with Periwinkle. They told the story of two fairies who met and fell in love, one of them was a winter fairy [Lord Milori], and the other was from the warm world [Queen Clarion]. They usually met every sunset at the border, where Spring touches Winter. But as their love grew stronger, they wish to be together and share each others worlds. So they disregarded the danger across the border. One of them [Lord Milori] broke a wing, for which there is no cure. And from that day, Queen Clarion decreed that fairies must never again cross the border, and Lord Milori agreed, that their worlds, should forever remain apart. Just as the Queen finishes her side of the tale, it begins to freeze in the Autumn Woods and Springtime Square, causing a commotion. Queen Clarion, Tink, Iridessa, Rosetta, Vidia, Fawn, and the Ministers (except for the Minister of Winter) arrive at the stream to find Clank and Bobble attempting to free the snow-maker. Finally, they succeeded in pushing the machine into the water, but Vidia realizes that it isn't over. The seasons become thrown out of balance, and the life of the Pixie Dust Tree comes into question; if it becomes too cold, it will freeze and stop producing pixie dust. Queen Clarion then proclaims that life in Pixie Hollow will change forever, and no fairy will ever fly again.
All warm fairies did everything they can to save the Pixie Dust Tree - the tinker-talents placing the leaf blankets on each branch of the tree, the animal-talents evacuate the frogs into a safer place, Iridessa evacuates the fireflies on one of the beriwinkles of Rosetta and Silvermist evacuates the snail into a safer place and Tink evacuating some animals on her house. Tink then notices that a flower that Periwinkle had planted is still blooming, despite its warm surroundings. Tinker Bell flies straight to the Winter Woods, and asks Gliss and Periwinkle why the flower was still alive. Gliss explains that frost tucks warm air inside, and Periwinkle suggests that they could frost the Pixie Dust Tree before the freeze comes. Tinker Bell and the frost fairies fly to the Pixie Dust Tree.
Meanwhile, at the tree, Bobble and Clank tried to place some blankets on a branch of the tree, but the strong winds blew them away, Clank says that the plan isn't working well and Bobble explains that the wind is strong and blew the blankets away. To the Queen's fear and disappontment, Tink, Peri, Gliss and Spike arrived. They explained the power of their frost to Queen Clarion, and they get right to work, but Spike realizes that the job would be too big for them to finish in time. Then Tinker Bell spotted Dewey, Lord Milori, and the rest of the frost fairies flying toward them, helping them frost the tree. Lord Milori ordered some winter-talents to spread to spring, summer and autumn and the rest to the Pixie Dust Tree.
Accomplished of frosting the whole Hollow, Lord Milori states that they've started all they can. He then warns the warm fairies that the freeze is upon them and they must take cover. Peri hopes that the scheme will work. Queen Clarion then asks Lord Milori that if everything will be alright, and Lord Milori states that he has no idea, for he never saw such calamity like this, Queen Clarion, trying to survive the cold, Lord Milori then cover Clarion with his snowy-owl feather cape to Queen Clarion. Lord Milori then orders all the winter fairies to stand guard all over the Pixie Dust Tree, awaiting the freeze to attack the tree.
Afraid the freeze had come too late, the fairies gather anxiously around the Pixie Dust Well, and rejoice when pixie dust then begins to flow again. The fairies of all talents, warm or cold enjoyed the celebration, but when Periwinkle invited Tinker Bell, Tink realizes that she had broke her right wing when she flew to the Winter Woods. Peri asked her why, but she said they've got to save the tree and ignores it because there was no cure for a broken wing, and warns Periwinkle to go back to the Winter Woods before her wings wilt. As the sisters hold hands and say good-bye, they reunite their wings and an explosion of pure sparkly light bursts from their wings, slowly magically healing Tink's broken wing. Queen Clarion and Lord Milori then reveal that they were the two lovers from the story and stay together as a couple.
From that day on, warm fairies can cross over the border into the Winter Woods anytime they like. A coat of frost keeps the warm fairy's wings safe while in the cold. Strong and close friendships between warm fairies and winter fairies blossom just as warm and beautiful as Periwinkle's flower and in the end of the film, Rosetta and Sled admit their mutually strong romantic feelings to each other.