A simple peasant by birth, William Thatcher leaves London when he is just seven to become a squire for Sir Ector. William and the two other squires, Watt and Roland, work faithfully for Sir Ector as they grow up. During a jousting tournament, Sir Ector gets struck and killed. Starving and penniless, William decides to take the risk and ride in his place. When he is pronounced tournament champion, they realize that it can be done. You can change your stars. After Watt and Roland are convinced, they set out to help William improve his technique. After a month of practice, they start for the next tournament in Rouen. Along the way, they meet Geoffrey Chaucer, a poor writer with a massive gambling problem. He agrees to write patents of nobility for William and act as his herald. Needing a lordly name, William goes by Sir Ulrich von Liechtenstein of Gelderland.
Upon reaching Rouen, William rides down the street surveying the town. His eyes rest upon a beautiful young lady. He pursues her and begs her name. She will not give it to him, and he is chased away by a group of over-pious priests.
At the tournament, William performs admirably in the sword arena, and is pronounced champion. In the joust, however, he does not win. He is beaten by Adhemar, a strong knight with intensely dark eyes.
William vows to focus all his energies on jousting and beating Adhemar. In the meantime, he becomes friendly with Jocelyn, as he learns she is called. She notices he is different than the other knights, not nearly as egotistic and very determined, and loves him for it.
Then, to Williams misfortune, Adhemar is called away to war, as he is the leader of the Free Companies. William goes to tournament after tournament and wins them all, but he is not satisfied because he still has not faced Adhemar and won. As they continue to win, William and his companions acquire glory and riches, in the form of horses, trophies, and of course, Jocelyn.
Jocelyn asks William to lose on purpose. Being the extremely smart female that she is, she knows that it will truly test his love for her and go against his self love. It works, and he starts losing. Then, after he has taken much beating, she sends word that if he loves her, he will win the tournament. Utterly confused by the female mind, he starts winning and beats out all the knights to become champion.
The location of the next tournament is none other than London, Williams hometown. He is excited by the prospect of being back, though he does not think that his father could possibly still be alive after all these years. He goes back to the house where he was born, and after talking to a little girl outside, goes in and finds his father, blind but still alive. They have a joyful reunion and talk well into the night. As William climbs on the roof of his father's house to fix a leak for him, he is watched by none other than Adhemar.
The next day, William is scheduled to joust against Adhemar; both are very eager to face the other and both are ready to beat the other. Right before he goes out, Geoff tells him that he cannot joust. Adhemar, being the coward that he is, told the tournament authorities. They took him away and placed him in the stocks where he was mocked and jeered by all the people who had only the day before cheered for him. Amidst the flying tomatoes and cabbage, a tall, cloaked person appeared surrounded by others. As he through back his hood and drew his sword, all could see that he was Edward, the Black Prince of Wales and heir to the throne of England. Repaying William for an early kindness showed to him, he frees him and knights him, Sir William Thatcher.
William is taken directly to the stadium where a furious Adhemar is waiting. They joust, and though Adhemar cheats by tipping his lance, William still earns a decisive victory over him. Adhemar is also is unhorsed by William, which adds to his shame because that had never happened to him before.
So, in this way William accomplished the unthinkable and rose above his humble birth to become the jousting champion of all England. He could not have done it without the faithful support of his father and his friends.