There is a pause in the battle. The King tells Prince Hal, who is bleeding from superficial wounds, to go back to his tent. But Prince Hal refuses. Prince Hal's younger brother John says they pause too long, and should go back out to the battle. He exits, accompanied by Westmoreland.
Prince Hal praises the courage of his brother and exits. This leaves the King alone, and he is set upon by Douglas, who does not know whether he is the real King or not. As they fight, Douglas gets the upper hand, and the King is in danger. But then Prince Hal comes to his father's rescue and drives Douglas off. The relieved King tells his son that he has redeemed his reputation with this rescue.
The King exits, and Hotspur enters. He and Prince Hal fight. Falstaff enters and watches the fight, but is then waylaid by Douglas. Falstaff falls down and pretends to be dead. Meanwhile, the Prince is victorious, killing Hotspur. The Prince speaks graciously to his enemy's corpse. He calls Hotspur a "great heart," and says the ignominy of his rebellion will sleep with him in the grave but will not be remembered in his epitaph.
The Prince then sees Falstaff lying on the ground, and assumes he is dead. He bids him farewell, and affectionately says it would have been easier for him to have lost a better man. The Prince exits, after which Falstaff gets up. He says he had to counterfeit death or Douglas would have killed him. He is pleased he has managed to save his life. Then he sees Hotspur's body and is afraid. What if Hotspur is merely counterfeiting death too? Falstaff stabs him in the thigh just to make sure. Then he hoists Hotspur on his back, intending to claim that it was he who killed him.
At that moment, Prince Hal and Prince John enter. They see Falstaff. John reminds his brother that he told him Falstaff was dead. Prince Hal swears that he did indeed see Falstaff lying bleeding and apparently dead on the ground. He wonders whether his eyes are playing tricks with him.
Falstaff confirms that he is indeed Sir Jack, and then he claims that he killed Hotspur and expects an elevation of his status to earl or duke.
The Prince exclaims that he killed Hotspur himself, and saw Falstaff dead. Falstaff replies that he was only temporarily down and out of breath, as was Hotspur. Then they rose up and fought for an hour. He swears that it was he who gave Hotspur the wound in his leg (which of course is true).
The Prince graciously does not challenge him about his lies.
The trumpet sounds a retreat, and Prince Hal knows they have won the battle. He and his brother exit, leaving Falstaff alone. Not for the first time, he promises to reform himself should he receive the earldom or dukedom he wishes for.
The play has been much concerned with the legitimacy of kingship. Both the King and the rebels have made long speeches justifying their positions and claiming that they are in the right. The fact that on the battlefield, the King has dressed many of his soldiers to look like the King symbolically highlights this question. But in this scene Shakespeare gives the audience a firm clue that Henry IV is indeed the legitimate King. It occurs when Douglas comes upon the King in the battle. At first he thinks the King is a "counterfeit," but then he says, "And yet, in faith, thou bearest thee like a king" (line 35). This is an indication, even more forceful because it comes from an enemy, of the King's true status.
This scene also contains some visual symbolism. After Prince Hal has killed Hotspur, he notices Falstaff lying apparently dead on the ground. These two men represent what Hal has had to defeat or cast off in order to be a worthy heir to the throne-Hotspur with his pride and impetuous heroics, and Falstaff for his continual bad influence on the Prince's lifestyle. The progress of the Prince is therefore clearly visible, in symbolic form, in this moment.