The first installment in the Croswald series is set in a magical world where scrivenists, scholars who wield enchanted quills, serve royal families whose power derives from magical stones set into crowns. A prologue introduces Derwin Edgar Night, a young scrivenist departing the scrivenist training Town on his Day of Ordination, the ceremony marking his graduation and service assignment. He cannot hold the family's name in his mind. Arriving at their grand but decaying castle, he finds it deserted. Dark fog transports him to a cliffside where he finds a wrecked carriage with no survivors and a wooden box emitting pulsing white light.
The main narrative follows Ivy Lovely, a fifteen-year-old orphan who works as the scaldrony maid at Castle Plum, tending fire-breathing scaldron dragons used for cooking. Each night she escapes to a hilltop overlooking fields of slurry blossoms, a flower that dampens magic. Her only friend, Rimbrick, an ancient woods dwarf, brings her books and tells her she shares traits with scrivenists: a photographic memory and a compulsive urge to sketch. He recounts a story about a dwarf who cursed a prince's family to wander endlessly from their castle, and urges Ivy to leave the slurry fields.
After being fired from Castle Plum, Ivy finds a farewell letter from Rimbrick admitting he owes her family a debt. Chasing an escaped scaldron past the slurry boundary, she triggers a sonic boom, as though the world bends toward her. A cabby, a carriage towed through the sky by a beast concealed within its own storm, crashes nearby. Inside, Ivy meets Lionel Lugg, the admissions officer for the Halls of Ivy, a school where young royals and sqwinches, aspiring scrivenists, train in magic. Lionel presents her with an enrollment invitation. The last item on her supply list is handwritten: a Kallegulous Key, which locks away anything or anyone while erasing all outside memory of the imprisoned. The cabby outruns the Cloaked Brood, the Dark Queen's henchmen, and deposits Ivy in Ravenshollow.
In town, the shopkeeper Mr. Munson warns Ivy to keep the Kallegulous Key hidden, especially from the Dark Queen, who has made an unprecedented visit. That evening, quills near the Halls swarm around Ivy, herding her toward the school. She forces open a gate with a beam of light and recognizes the Halls as the castle from her recurring dream, which features a vast library of blank books and a silent, faceless man. The school matches her dreams in most respects, though the library's books contain words and the mysterious man is absent.
In Professor Fenix's glanageries class, where students enter magical bottles that bring imagined scenarios to life, Ivy is transported not to Fenix's scene but to an old schooner called The Wanderer. She discovers a journal by Derwin Edgar Night filled with sketches of a Kindred Stone, a mysterious magical artifact. When she returns still clutching the journal, an object that should not cross from imagination to reality, the Selector, the school's headmistress, orders it locked in the Forgotten Room using a Kallegulous Key. Once the door closes, everyone forgets the incident, but Ivy retains full memory.
Through a hidden passage, Ivy discovers Winsome Monocle, an elderly retired scrivenist and alcheturist (a specialist in dangerous potions) living secretly in a tower. Winsome served the Wandering Family, the cursed royal house, under the Wandering Curse, the forgetfulness hex from Rimbrick's tale, and was released sixteen years ago. Ivy studies with him during free periods, learning more from Winsome than in most classes. Meanwhile, Rebecca, a royal whose Hellexor Stone involuntarily transforms her into animals, becomes Ivy's roommate and closest friend.
Driven by the memory only she retains, Ivy brews a distraction potion, steals the Kallegulous Key, and breaks into the Forgotten Room. Inside she finds a map marked "We hide her here" with the slurry fields circled, forgotten scrivenist portraits, and Derwin's books. She memorizes the journal's sketches but leaves it behind. A violent wind sweeps Ivy out, but Rebecca is trapped when the door slams shut, and her existence is erased from all memory. Rebecca eventually escapes by using her stone's power to become a bird and fly out when the door is opened again.
Winsome reveals that Ivy's magic far exceeds an ordinary sqwinch's. He shows her sketches of the dream castle drawn by Derwin, nearly identical to her own, and confirms the man in her visions is Derwin. He asks Ivy to help find Derwin but warns he is overdue for the Hollow Shaft, a sacred repository where exceptional scrivenists' knowledge is preserved after they die in a process called turning tome.
Ivy sneaks to the Hollow Shaft with Fyn Greeley, a third-year class facilitator. A preserved scrivenist's voice tells the story of Princess Isabella, Ivy's royal ancestor, who befriended Rimbrick. When Isabella opened a magical bottle from Rimbrick prematurely, a dark entity escaped and she lay dying. Rimbrick channeled powerful magic into her heart, sending a burst of light skyward that doubled the moon's size and created a shining stone on Isabella's chest. After a harrowing return, the Selector bans Ivy from the end-of-year Masquerade Ball.
In the glanagerie final, the captain of The Wanderer presses a letter into Ivy's hand: "I am locked in by the evil one's imagination. We need each other to end this." Ivy suspects the captain is a real person trapped in a glanagerie bottle. Before the Ball, Ivy discovers Winsome's tower empty and his Hollow Shaft summons torn open; he has departed without farewell.
Defying the ban, Ivy attends the Ball. The Dark Queen floods the ballroom with enchanted water, traps students in an underwater trance, and demands Ivy's crown and blood. She reveals she killed Ivy's parents and Isabella, and that Ivy is the last heir to the queenly line. Ivy creates air bubbles for drowning students and enters a vision, following the dream figure to the Forgotten Room. The Wanderer crashes through the ballroom on a massive wave, shattering the enchantment. Winsome clings to the bow, shouting that Ivy freed the captain, before a burst of gold light consumes him. The Dark Queen flees. The captain introduces himself as Derwin Edgar Night, Ivy's parents' scrivenist.
The next morning, Derwin meets Ivy in the Den and addresses her as "Your Highness." He explains that Winsome died saving Ivy by physically opening the Forgotten Room while Ivy opened it through her vision, summoning the ship from its bottle. An ancient family tree confirms Ivy is the last heir to the queenly bloodline. The Wandering Curse made her family invisible to the Dark Queen until the Cloaked Brood killed Ivy's parents and grandfather in the carriage wreck Derwin discovered in the prologue. Winsome hid baby Ivy in the slurry fields, the one place her magic would go undetected. Ivy was born under a double moon: At her birth, the light containing the magic Isabella's heart had sent skyward consolidated into a beam aimed at the baby's heart, and the double moon vanished.
Derwin gives Ivy the wooden box from the prologue, now opened to reveal a fragment of the Kindred Stone, the first magical stone, created from Isabella's heart. He broke the stone into three pieces before his imprisonment. The Dark Queen, he explains, is not human but a perversion born from a glanagerie experiment. Warning that someone inside the school allowed the Queen access, Derwin directs Ivy to Belzebuthe, the scrivenist training Town, setting up the next installment in the series.