In a world where magic is outlawed in all four kingdoms, the fairy Madame Weatherberry enchants the castle staff of the elderly King Champion XIV to secure a private audience. She argues that the world has wrongly conflated magic, a pure art practiced by fairies, with witchcraft, a destructive practice, and proposes an academy to train young fairies to help people and win public acceptance. To pressure the king, she warns of a classified "Northern Conflict" devastating King Nobleton's realm that could spread south, making trained fairies invaluable. Champion, who abolished the death penalty for magic after his own mother was beheaded on a false charge, grants permission to recruit two students, provided she obtains guardians' written consent.
Fourteen-year-old Brystal Evergreen lives in the countryside near Chariot Hills in the Southern Kingdom, where women are forbidden from reading or pursuing education. Her domineering father, Justice Evergreen, heads the family; her anxious brother Barrie is studying law; and her cruel older brother Brooks is already a Deputy Justice. Brystal secretly reads books supplied by Barrie. When she publicly corrects Brooks for feeding Barrie false information before a law examination, Justice Evergreen erupts, threatening to throw her out. After an emotional breakdown in the town square, Brystal spots a help-wanted sign at the Chariot Hills Library, applies under a false name, and is hired for evening cleaning shifts, gaining access to thousands of books.
On the library's second floor, Brystal discovers a hidden room marked "JUSTICES ONLY," filled with banned books revealing how the Justices tracked and executed authors who exposed corruption and the oppression of women. The last book is
The Truth About Magic by Celeste Weatherberry, containing incantations to test whether the reader possesses magic. When Brystal reads the fairy incantation aloud, hundreds of flowers burst from the walls. She returns days later and fills the room with glowing orbs, but the librarian and two guards catch her. She is arrested for trespassing, female literacy, and committing magic.
At trial, the vindictive Justice Oldragaid assigns Barrie as prosecutor without revealing the defendant is his sister. Unaware, Barrie recommends the maximum penalty, unwittingly sealing a death sentence. Justice Evergreen bursts in with an order from a superior overruling the sentence, and Brystal is sent to the Bootstrap Correctional Facility for Troubled Young Women, a crumbling institution where the hypocritical Mr. and Mrs. Edgar exploit inmates through forced labor. Her father disowns her as she is dragged away. There, Brystal befriends Pip Squeak, a young girl imprisoned since toddlerhood for her ability to squeeze through narrow spaces. When Pip is caught stealing a blanket for Brystal, Brystal takes the blame and accidentally conjures a flock of birds that attacks the staff.
Before Brystal is punished, Madame Weatherberry arrives bearing King Champion's authorization and frees her. She shows Brystal a Map of Magic, which displays every fairy and witch in the world as twinkling stars, and reveals that Brystal is one of the brightest. They travel to the Evergreen home, where Justice Evergreen refuses permission. As they leave, Mrs. Evergreen secretly slips her daughter the signed permission form, which requires only one parent's signature, and urges her to find happiness.
Madame Weatherberry recruits two more students. Xanthous Hayfield is an 11-year-old boy whose body produces uncontrollable fire; he accidentally killed his father and burned down their home after being beaten. Madame Weatherberry gives him a Muter Medal, a crystal device that suppresses his flames. Emerelda Stone, a 12-year-old girl raised by dwarfs in a coal mine, can transform coal into gemstones. She initially refuses, distrustful of humankind, but Brystal persuades her.
The students pass through a magical hedge barrier into the academy's hidden estate: colorful wildflowers, crystal lakes, and a golden castle overlooking the ocean. They meet Mrs. Vee, the housekeeper, and Madame Weatherberry's apprentices, Tangerina Turkin, who controls bees, and Skylene Lavenders, whose body flows with water. A fourth student, 13-year-old Lucy Goose, arrives when her musician parents abandon her on her birthday, unable to handle her destructive paranormal abilities. Brystal bakes Lucy a birthday cake and befriends her.
Lessons begin. Brystal consistently produces results far beyond her intentions, once transforming all the leaves on a tree into butterflies when trying to change a twig into a caterpillar. Madame Weatherberry diagnoses her with "magiclexia," a block caused by years of suppressing magic, and gives her an ancient crystal wand. When Brystal touches it, her star on the Map of Magic grows to rival Madame Weatherberry's.
Throughout this period, Madame Weatherberry receives mysterious black envelopes and periodically leaves, claiming to visit a sick friend. Four cloaked witches visit and pressure her to return to the Northern Kingdom. Through a hole in her bedroom wall, Brystal eavesdrops and learns Madame Weatherberry is fighting the Northern Conflict. Each time Madame Weatherberry returns, she appears more aged and weakened. She privately confirms to Brystal that she has been fighting the Snow Queen, a powerful witch devastating the Northern Kingdom, and asks Brystal to make two promises: to take over the academy if she dies, and to kill the Snow Queen if she cannot. Brystal reluctantly agrees.
After a fight with Tangerina, Lucy runs away into the In-Between, the dangerous neutral forest between kingdoms. Brystal follows, and both are nearly killed by witch hunters before a mysterious armored knight named Horence, a supernatural guardian spirit bound to the academy's grounds, saves them. Using incantations from
The Truth About Magic, Brystal later proves Lucy is a fairy, not a witch, ending Lucy's identity crisis. The classmates make a pact to always support and protect one another.
Madame Weatherberry departs one final time. Snow begins falling on the academy grounds, signaling the Snow Queen's power is spreading. Brystal leads her classmates north into the In-Between. They fall into Greenhouse Canyon, where a Sorceress reveals a truth contradicting Madame Weatherberry's teaching: No one is born a fairy or a witch; it is a choice. A magical Tree of Truth confirms that Madame Weatherberry lied to protect the community and reveals she has been captured and imprisoned in Tinzel Palace.
The students emerge at the base of the Northern Mountains, where General White, commander of the Northern Kingdom's remaining army, fights with his last soldiers. The four witches stand at the Snow Queen's side, having betrayed Madame Weatherberry. In the battle, four students each neutralize one witch. When the Snow Queen summons an avalanche, Xanthous channels all his repressed pain into a massive blast of fire that vaporizes it. Brystal sneaks into Tinzel Palace and confronts the Snow Queen, only to discover the witch is Madame Weatherberry herself. The fairy's real name is Snowy Celeste Weatherberry; the Snow Queen is a manifestation of her lifelong suppressed rage, accessed through an icicle scepter. She created the Snow Queen persona to give humanity a threat only fairies could resolve, but the plan spiraled beyond her control.
Madame Weatherberry begs Brystal to kill her. Brystal refuses, arguing that destroying the Snow Queen would remove humanity's reason to respect fairies. She proposes Madame Weatherberry retreat deep into the mountains, keeping the Snow Queen alive as a lingering threat. The fairy agrees, telling Brystal to watch for northern lights as a signal she is still winning the internal fight. Brystal tells her classmates that Madame Weatherberry perished while forcing the Snow Queen into seclusion.
After the global blizzard subsides, Brystal and her classmates present themselves to King Champion as the "Fairy Council" and deliver demands: legalizing magic, freeing magical prisoners, granting women equal rights to education and employment, and reprinting all banned books. The king and the other kingdoms' rulers agree. Brystal renames the school the Celeste Weatherberry Memorial Academy of Magic. Unicorns transport the young women from the Bootstrap Correctional Facility to the academy, reuniting Brystal with Pip. Hundreds of members of the magical community stream onto the grounds. Lucy identifies Brystal's magical specialty as compassion. Brystal sees northern lights glimmering in the mountains, confirming Madame Weatherberry is still fighting, and addresses the gathered community, urging them to live freely and declaring that the tale of magic deserves a happy ending.