Wild Magic is set in the same world as The Song of the Lioness quartet. Daine's family was killed earlier in the year by raiders and after enacting revenge upon the raiders, she runs away to find a new life. She gets a job as an assistant to the horsemistress of Tortall's Queen's Riders, and she learns new things about herself and gains a new family.
The reader is introduced to Daine, a thirteen year old girl who can speak to animals. Daine meets Onua Chamtong, the woman in charge of the horses for the "Queen's Riders," and is hired to help bring up a group of new ponies to the capital of Tortall, Corus.
Along the way, Daine and Onua are attacked by strange creatures called immortals and later learns that nearly all of Tortall is being plagued by them. However, the immortals that attacked had been on the chase of a hawk, but not just any hawk. The hawk later turns out to be the powerful mage, Numair Salmalín. She also meets Alanna the Lioness. Upon reaching Corus, she continues as the assistant horsemistress, teaching Rider trainees and learning more about her own powers of "wild magic" (here she meets Evin Larse, who appears later in the Protector of the Small quartet).
On their way to summer camp at Pirate's Swoop, Daine, to continue her training in her wild magic, tells Onua and Numair about how she had lost her mind after the murder of her family and joined a pack of wolves to kill the bandits who had killed her family. The townspeople of Snowsdale then realized what was happening and tried to kill her, so she fled. After time, with the help of her only family left, Cloud, a pony, she gained her humanity and sanity. Relieved that her friends still like her, and after Numair, her mage teacher, enacts a spell so she will not lose her mind once again, she begins to hone her powers and soon learns to heal animals. Towards the end of the book, she saves Pirate's Swoop from an attack of pirates and immortals from Carthak. She's also left in charge of a dragonet, whos mother has died in the battle to help save Tortall. Daine nicknames the dragonet Kitten, her real name being Skysong.