King Edward’s doctor has given him less than a year to live. Lord John Dudley, his counselor, urges Edward to amend his will so that neither of his sisters, Mary or Elizabeth, will succeed him. Mary is a Verity, which means she believes animal magic is evil and should be destroyed.
As many people are Edians, humans able to transform into animals, this would cause a civil war in the country. Elizabeth’s true allegiances are unknown, so Lord Dudley convinces Edward to name his cousin, Lady Jane Grey, his successor. Jane has been Edward’s closest friend, and he knows she is a proponent of Edians.
As Edward does not believe a woman should rule England, however, it is decided Jane should marry so that her son may become the next king. Lord Dudley arranges for her to wed his son, Gifford. He admits to the king that Gifford or G, as he prefers to be called, is a cursed Edian. He transforms into a horse every morning at sunrise and is unable to transform back until sundown. Neither man has the courage to tell Jane about G’s curse.
When Jane’s mother tells her of the upcoming wedding, Jane takes a secret trip to the Dudley estate to meet her fiancé. As G is a horse, he is, of course, unable to see her. His brother makes some crude comments, suggesting that G is a womanizer, which infuriates Jane. Despite her objections to the wedding, she is forced to go through with the ceremony.
In an effort to get the courage to tell Jane of his curse, G gets drunk at the reception. He and Jane argue before going to bed, and G passes out on the floor. Jane is shocked when he transforms into a horse at daybreak and upset to learn that unlike most Edians, cannot change back to his human form at will.
Edward’s health worsens once he signs the succession decree. One afternoon, as he tries to eat pie, his dog — named Pet — snarls and causes the pie to fall to the floor. Instead of eating it, Pet prevents Edward’s nurse from trying to feed him more.
When his nurse leaves his room in fear, Peter Bannister, the stable master, arrives. He speaks to Pet and convinces her it is safe for her to transform. Edward is flabbergasted when his favorite dog, whom he has slept with, morphs into a naked young woman. Pet, or Petunia, is Peter’s daughter. She has been a dog for so long it is difficult for her to maintain a human form.
She tells the king his food is being poisoned and that is why he is ill. It seems his doctor, Lord Dudley, and his nurse are in league to kill him. Pet transforms back into his dog and warns him later in the day that the food Mary offers him is also poisoned. His sister Elizabeth, called Bess, gives him apricots to eat, and Pet assures him they are fine. Bess also tells him that she knows of the plot and will try to help him.
Edward needs to discover his Edian form and use it to flee the castle and find his grandmother. Gran was banished because Edians were outlawed at the time, and she could transform to a skunk. When soldiers come to kill him, Edward jumps from his bedroom window and turns into a kestrel. Dudley proclaims that the king has died.
Jane and G are hurried off to a country estate where they are kept away from Edward and court machinations. Jane is at first furious when G prevents her from trying to keep a pack of wolves from attacking the cow of a starving village. Later, G explains that the wolves were part of The Pack, a band of rogue Edians that create havoc in the country.
Jane’s anger lessens, but she expresses her desire to help the villagers who were hurt in the struggle. G agrees, and the two of them head out in secret. Jane, an avid reader, has learned a great many herbal remedies to heal cuts and prevent infections. Between her ministrations and the food they bring, she and G earn the respect and friendship of the villagers.
Jane and G bond over their desire to help others, and soon their relationship turns romantic. But before they can act on their new feelings, messengers arrive with the news that Edward is dead and Jane is now Queen of England.
Edward cannot control his Edian form and finds himself lost in the woods. He meets a young commoner named Gracie, who can transform into a fox. Gracie is beautiful, confident and strong, and Edward falls in love with her. She is at first standoffish as she is Scottish, and Britain has been at war with her people for years. Soon she is drawn to Edward’s helplessness and good heart, however, and agrees to take him to his grandmother’s house.
As the poison continues to work through his body, Gracie convinces him to turn into a kestrel so she can carry him to safety. Once they arrive, Gran nurses him back to health. As he continues to improve, Gran and Bess convince him he must go to France to secure help and soldiers so he can regain his crown.
Jane and G argue when she announces that she will not make G her king. While G spends his time away from the castle as a horse, he learns that Mary is mustering an army to take Jane’s crown. Before he can warn her, the army arrives. Guards take Jane prisoner as G transforms into a horse. Mary orders him burned at the stake.
In her cell, Jane falls into despair. In her desperation to see G again, she suddenly transforms into a ferret. She steals the key from the guards and brings it to G so he can escape. G carries her to the stables so they can steal a horse. They encounter Peter Bannister, who helps them saddle a horse and directs them to follow Pet as she sniffs out Edward’s whereabouts.
Looking for food, G stops at a tavern, while Jane is in her ferret form. Unfortunately, this tavern is headquarters of The Pack. They do not take kindly to strangers. Before G can leave, Jane is spotted. The members of The Pack want to eat her. She is stepped on before G can escape. G and Pet hurry to carry Jane, who is severely wounded, to Gran’s house. They arrive safely and Gran is able to heal Jane’s injuries.
Edward is thrilled to have his favorite cousin by his side as he begins his quest to regain his throne. Gran tries to instruct Jane and G how to control their transformations so they can morph at will, but they are unsuccessful. Edward decides to try and get the backing of The Pack to help him overthrow Mary.
Their leader, Archer, will only do so if Edward will kill the Great White Bear of Rhyl. The creature is huge, but Edward and G devise a plan and kill the bear. Edward secures the Edians’ help. Then Edward and the others set off to gain France’s aide. Edward manages to charm his former fiancé — Mary, Queen of Scots — and she agrees to give him her secret army of Scottish Edian soldiers while the French king will give him ships and more soldiers.
Edward returns and marches on London. Jane devises a plan where the armies create a diversion while she, Edward and G sneak into the castle to confront Mary. They first encounter Lord Dudley and Bash, the weapons master. Edward fights Bash while G and Jane take on Lord Dudley. Eventually, they are able to subdue the men and leave them tied up so they cannot foil their plans.
Edward faces Mary, and guards lead her away to prison. But once the crown is his again, Edward realizes he does not want it. Instead, he gives it to Bess. He finds Gracie and the two finally share a kiss, and it seems, will live out their lives together.
Jane and G, who have learned through their love to control their transformations, renew their vows at a lavish wedding ceremony. That night, G admits that he never was promiscuous. His late nights had been spent at poetry readings. He reads a love poem he wrote for her. After they share several passionate kisses, the reader is told that they consummate their marriage.