The Hero and the Crown is the story of Aerin, princess of a fantasy realm, and her growth from a weak and frightened girl into a powerful and decisive warrior queen. Aerin is born to a king and a witch, making her acceptance at court dubious, and she seeks acceptance in martial prowess and other pursuits. She is eventually drawn into an epic quest involving the slaying of an ancient and malignant dragon, Maur.
Aerin is the only child of Arlbeth, king of Damar, and his second wife. Aerin inherits her mother's pale skin and fiery red hair, setting her apart from all other Damarians (who are dark-haired and dark-skinned) and causing her to be feared and ostracized by them. It is rumored, possibly correctly, that Aerin's mother was a witchwoman and she made Arlbeth fall in love with and marry her by magically enchanting him, so that she might bear an heir to rule Damar. However, when she saw that it was a girl that she had born rather than a boy she died of despair.
While the king and the first sola, Tor, supported Aerin, some of the royal family, especially Galanna, a beautiful, but vain young woman, hated her. They went so far as to suggest that her mother was unfaithful, that she is not truly Arlbeth's daughter. This idea is supported by the fact that Aerin failed to develop the Gift, known as kelar , an ability to use magic that all members of the royal family inherit to some degree. During one of her regular fights with Aerin, Galanna convinces her to eat the leaves of the surka plant, known to aid the magic of those of the royal blood, but poisonous to all those not of royal blood. Aerin takes up to the challenge, eats a branch full of leaves and promptly starts to feel ill. While the surka plant does not kill Aerin, it makes her extremely ill, affecting her condition for many years. The one single surka leaf can sometimes kill the consumer and one can safely assume that Aerin is Arlbeth's child since she did survive eating all the surka leaves.
Aerin stumbles upon a book about the history of Damar and the dragons of old that used to terrorize it, of which only much smaller relatives still exist. Finding privacy in the pasture of her father's now-injured war horse, Talat, Aerin reads through the book while forging a friendship with him. At the back of the book she finds a recipe for kenet, an ointment meant to protect the wearer from the effects of fire. Unfortunately, the recipe does not specify the amounts of each ingredient needed. While her first attempts to make the ointment fail, Aerin begins to split her time between learning to ride Talat and experimenting with the fire-proof ointment. After three years of experimenting, Aerin stumbles on the correct proportion of ingredients, successfully making kenet. Then, Aerin goes off to slay a small dragon that is terrorizing a village with the help of her kenet and Talat.
While Aerin continues her role as dragon killer, trouble comes from the north, spreading madness to one of the western barons, Nyrlol, who is threatening civil war.
Arlbeth fears that the hero's crown, an item of power, has finally fallen into the hands of the Northerners. Arlbeth is forced to ride north with many of his court to deal with Nyrlol, whose behavior he believes to be a symptom of the growing power of the North, but denies Aerin her request to join him in the journey, because his people do not trust her. However, just as Arlbeth prepares to ride north, a messenger arrives bearing news that the last of great dragons, Maur, has reappeared and is terrorizing Damar. Arlbeth has no choice but to leave Maur until he deals with Nyrlol. But Aerin, having been left behind, decides to go fight Maur on her own.
Aerin just barely manages to defeat Maur, claiming a red stone left behind when his body burns itself to ashes as her trophy, but the fire of the great dragon proved too much for her kenet. Aerin is left badly burned and with a broken ankle, yet manages to drag herself onto Talat, who carries her home. She is intercepted by Arlbeth, Tor and their company as they return, and carried back to the castle. After many weeks of rest and care Aerin's health has not improved. Maur's skull is brought to the castle as a trophy but its presence seems to taunt Aerin. In her declining state, Aerin dreams of a blond man by a lake who beckons her to come to him so that he may help her. Aerin, after much thought, leaves Tor a note and rides off on Talat to find this man.
As if guided by an external force, both Aerin and Talat seem to know exactly where to find the man by the lake. He reveals himself as Luthe, and heals Aerin by placing her in the Lake of Dreams, which causes her to become not-quite-mortal. Luthe teaches her some magic and Aerin learns that it is kelar in the royal blood that gives them their magical abilities. The kelar comes from ancestors in the north and is what gave them the power to become rulers of Damar. Luthe then reveals what he knows of her past. Aerin's mother and uncle, Agsded, along with Luthe, were students of a master mage. Agsded was the best student but used his ability for evil. A prophecy foretold that one of Agsded's own blood would defeat him, forcing Aerin's mother to flee to the south. She believed that only a son could defeat Agsded, yet Luthe tells Aerin this is not so, and, when she is fully recovered, sends her north with Gonturan, The Blue Sword, for protection.
As she travels north, Aerin is joined by armies of foltsza, large mountain cats, and yerigs, large wild dogs. They eventually reach Agsded's fortress. While Talat, the foltsza, and the yerigs help break an opening into the fortress, Aerin creates a wreath out of surka leaves and places the red rock that she had taken from Maur's body in it. Aerin climbs the long staircases to the top of the fortress where she faces Agsded, who is wearing the hero's crown. Gonturan protects her from Agsded's red sword, but Agsded proves also not mortal, with skin tougher than stone. Just as she is about to fail, she throws her wreath of surka, with the red stone, at him. It falls over Agsded and causes him to burn, defeating him. With his death, Agsded's fortress crumbles. Aerin is met by Luthe, who reveals to her that much time has passed in her battle with Agsded, something that she survived only because she is no longer mortal. Luthe "drags" her back to the present, where a yerig brings her the Hero's Crown. She also discovers that the red stone is Maur's bloodstone, a stone of great power. Aerin gives it to Luthe, saying she doesn't want to have any part of Maur, no matter how much power it would bring her.
Luthe escorts Aerin back as far as his lake on her way back home, becoming romantically involved in the process. Aerin leaves him but promises to return one day. Aerin continues back to find the kingdom losing in a battle with the Northerners. Using Gonturan and her army of foltsza and yerigs, and giving the Hero's Crown to Tor, she helps defeat the Northerners, but at the cost of many lives, including Arlbeth. Aerin, with Tor's help, finally rids the kingdom of Maur's skull, which had been polluting the thoughts of the people and helping in their defeat, but in the process the skull turns Damar into a desert. Aerin marries Tor, whom she truly loves in her own way, and they help rebuild the kingdom together as its rulers.