The play begins with the funeral of Henry V, which is interrupted by a message announcing trouble in France. Part of the English territory once won by Henry V has been lost, the Dauphin Charles has been crowned king, and the English general Lord Talbot has been taken prisoner. Hearing the news, the noblemen rise to action.
As Talbot’s forces lay siege to Orléans, Charles and his lords try to fight their way out. Despite being exhausted and starving, the English still beat them. Amidst the chaos, the Bastard of Orléans brings a young woman named Joan la Pucelle—also known as Joan of Arc—to meet Charles. She says she has seen visions and can lead the French troops to victory. Charles tests her by challenging her to single combat, and after she beats him, she assures the French that she will break the siege that very day.
In London, Gloucester, the Lord Protector who will rule until the young king is old enough to take over, comes to blows with the leader of the church, Bishop Winchester, at the Tower of London. Winchester bars Gloucester from entering the Tower and accuses him of plotting to take over the kingdom. Their servants join in the fight, but soon the Mayor arrives to split them up.
Back in France, Talbot has been released in exchange for a captured French lord. The French launch a sneak attack on the English forces, killing important leaders. Talbot and Joan meet in battle, and though she gains the upper hand, she lets him live, saying it isn’t his time to die. Joan succeeds in breaking the English siege, and the French nobles celebrate her success. But soon after, Talbot engineers a sneak attack on Orléans and retakes the city.
Meanwhile, in London, lords gather in the Temple Garden near the Inns of Court to dispute a point of law. Richard Plantagenet and Somerset form the heads of opposing camps, and they pluck white and red roses as symbols of their differing opinions. Their followers do the same. Somerset insults Plantagenet’s father, and they each scorn each other. Warwick predicts that the argument, though begun over something so small, will end in thousands of deaths.
Plantagenet then goes to the Tower of London to talk to his uncle Mortimer and to ask about his father. Mortimer says he was once in line for the throne and raised an army to help him claim his right to power, but he was captured and executed, while the rest of the Mortimer line, including this Mortimer, was suppressed. Mortimer bequeaths Plantagenet his title, then dies, leaving his new heir even more anxious to regain his birthright.
All of Parliament soon learns of Gloucester and Winchester’s dispute when their serving men crash into the room pelting each other with stones. King Henry orders them to stop fighting, for civil dissension will weaken the nation. The two men promise to stop fighting for the moment. Warwick then presents Plantagenet’s request to have his father’s title passed on to him. The king grants it, also giving him his uncle Mortimer’s former title, and, thus, renaming him the duke of York. Gloucester urges the king to go to France to deal with the unrest there, and Henry agrees.
Back in France, Talbot’s forces stand outside Rouen, prepared to attack. Although Rouen is a walled city, the English forces manage to beat the French. Joan tells Charles not to worry about the loss, because she has a new plan to weaken Talbot. Burgundy, a French leader fighting with Talbot, constitutes the only threat to her plan, but she lures him to the French camp and convinces him that he’s fighting for the wrong side.
Henry arrives in Paris with his nobles. Talbot goes to meet him, where he receives a message from Burgundy about his change of loyalty. Talbot goes with his forces to try to talk to him. Meanwhile, two underlings of York and Somerset ask the king for the right to have an armed fight. This is the first the king learns of the struggle between the followers of the white rose and the red rose. The king urges Somerset and York to put aside their differences while they are in France, for their dissension will make Britain appear weak to its enemy. The king says it shouldn’t matter what rose he wears, since he loves both his lords—yet even as he says this, he picks Somerset’s red rose. York is upset, but he keeps it to himself. Henry assigns the two men to new tasks in France, making York the leader of the English troops and putting Somerset in charge of the cavalry.
Meanwhile, Talbot prepares to attack Bordeaux, but the city is well defended, and as Charles’s forces approach from behind, he realizes he is trapped. A messenger from Talbot asks York to send the cavalry reinforcements, but York has no troops to send. Convinced Somerset has delayed the delivery of the cavalry out of dislike for him, York bemoans Talbot’s imminent death. The same messenger goes to Somerset, who says York is to blame for sending Talbot into battle without sufficient troops. The messenger says Talbot’s death will be both noblemen’s shame.
Talbot’s son John arrives on the battlefield, having come to learn about soldiering from his father. Talbot tells him to leave, but John refuses, saying he will disgrace the honor of the Talbot name if he flees. The battle begins, and John is wounded; yet still he will not flee. Finally, John is killed, and Talbot dies of grief. The English army is defeated.
Back in London, Gloucester reads letters from the pope urging the English to make peace with the French. Charles agrees to make an offer.
At the same time in France, Charles’s forces are under attack by the united front of Somerset and York. Joan summons an array of demonic “fiends” to assist her, but they refuse to help, leaving her to be captured by York. In the same battle, Suffolk captures Margaret of Anjou, who is the daughter of one of Charles’s nobles, René. Impressed with her beauty, he wants to woo her, but he is already married. He decides to woo her for Henry instead.
York and Warwick hold Joan in trial and interrogate her. She tries to convince them that they should not kill her, for she is a virgin and therefore able in her purity to communicate with wrathful powers that will come down on them if they execute her. York and Warwick nonetheless prepare to have her burned at the stake. She then claims that she is pregnant and that they wouldn’t dare kill a pregnant woman, but York tells her that no matter what she says, she will die. She curses the English and is led away.
At the same time, the newly promoted Cardinal Winchester tries to engineer peace between Charles and the English. At first, Charles resists, but his nobles advise him to accept the peace to stop the massacre of his citizens; they can always break the treaty later.
Meanwhile, Suffolk arrives in London and tells the king of Margaret’s charms. Gloucester reminds him he is already engaged to the daughter of a relative of Charles, a match that would soothe international politics. But even though a union with Margaret offers no political or material advantages, Henry decides to marry her anyway. Suffolk has succeeded; now Margaret will rule the king, and he will rule Margaret.