In the backdrop of a 14th-century European jousting tournament, three impoverished squires—William Thatcher, Roland, and Wat—find themselves grappling with the unexpected death of their master, Sir Ector. Their fate shifts dramatically when William, driven by sheer determination and a hint of audacity, dons the armor of his deceased lord to achieve triumph in the tournament, thus securing a prize that had previously seemed unattainable.
As time progresses, William becomes infatuated with the idea of contending against nobility, despite the stringent regulations that bar commoners from such tournaments. In contrast, his companions focus on cashing in on their newfound fortune and leaving the scene. Undeterred, William persuades Roland and Wat to remain and assist in polishing his skills, motivated by an intense desire to affirm his place among the elite.
Their adventure takes a surprising turn when they meet the down-and-out Geoffrey Chaucer, who agrees to forge a patent of nobility for William, allowing him to masquerade as Sir Ulrich von Liechtenstein from Gelderland. However, this deal bears a heavy burden, as Chaucer owes debts to Simon the Summoner and Peter the Pardoner, and William pledges to clear these obligations.
As the tournament progresses, William's armor experiences considerable wear and tear; in a display of his resourcefulness, he convinces Kate, a talented blacksmith, to repair it free of charge, further enhancing his reputation as a crafty and capable competitor. His success in the sword event enables him to alleviate Chaucer's debts, while his impressive jousting skills earn him a place in the final round of the tournament.
The event draws the attention of Jocelyn, a noblewoman who has caught William's eye, along with Count Adhemar of Anjou, who similarly vies for her affections. Although Adhemar initially gains the upper hand, William pledges to avenge his defeat, only to be met with the scornful words: > "You have been weighed, you have been measured, and you have been found wanting."
As Kate joins William's entourage, she crafts him lightweight armor, setting the stage for future victories. In the subsequent tournament, both William and Adhemar find themselves matched against Sir Thomas Colville, only to realize that their opponent is none other than Prince Edward, the heir to the English throne. While Adhemar opts to withdraw to avoid harming the prince, William decides to joust, earning Edward's respect for his bravery.
With Adhemar called away to battle, William seizes the moment to establish his prowess, notching numerous victories during Adhemar's absence. In a testament to his loyalty, William initially agrees to Jocelyn's request to lose deliberately; however, he ultimately resolves to win in her name, solidifying his love for her.
Upon arriving in London for the World Championship, a reflective flashback reveals William's humble origins, showcasing his choice to leave his father in pursuit of training alongside Sir Ector to reshape his destiny. Meanwhile, Adhemar reveals his scheming nature by announcing that he has arranged to marry Jocelyn with her father's approval. Despite William's remarkable performance at the tournament, he finds himself facing internal turmoil as he clandestinely visits his now-blind father, reopening old wounds.
As jealousy and deceit fuel Adhemar's actions, he alerts authorities to William's true identity, resulting in his swift capture and public humiliation in the pillory. Yet, William’s friends rally to support him, defending their champion against the enraged mob. Just as the situation reaches a boiling point, Prince Edward intervenes, recognizing William's unyielding honor and commitment to the ideals of knighthood.
Edward then dismantles the misconceptions surrounding William's heritage, declaring him a descendant of an ancient noble line. With this upheld revelation, he knights William as "Sir William," asserting that his status is indisputable as the Prince-royal. Following this dramatic twist, William returns to the tournament to confront Adhemar in a climactic showdown.
In a distressing turn of events, Adhemar resorts to underhanded tactics, utilizing an illegally sharpened lance to severely injure William. As his strength wanes and injuries accumulate, William must dig deep for every ounce of resilience to unseat Adhemar in a desperate attempt for victory. He requests a moment to disrobe from his armor, which leads Chaucer to provide a long-awaited introduction, setting the stage for this final confrontation.
As William charges during the climactic pass, he envisions his father and Jocelyn anxiously watching from the stands. Drawing strength from their presence, he secures Wat's help to fasten the lance to his arm, preparing for one momentous clash against Adhemar. In a surge of fierce determination, William calls out his true name as he rides forward, delivering a punishing blow that sends Adhemar crashing to the ground.
In the aftermath of this glorious victory, William and Jocelyn share an emotional embrace, celebrating amidst a jubilant crowd. In the midst of this victory, Chaucer reflects on the prospect of documenting their saga, heralding the dawn of an unforgettable chapter in their lives.
