King John hands his crown ceremoniously over to Pandolf. Representing the authority of the pope, Pandolf returns the crown to John, signifying that John now rules at the permission of the pope. John urges Pandolf to keep his end of the bargain to convince the French to give up their attack. Pandolf departs.
The Bastard enters to report the success of the French offensive. The French have won the countryside and are now in London, having been aided by John's nobles. John marvels that his nobles didn't return after Arthur was reported alive, but the Bastard reveals that Arthur was found dead. John falters, but the Bastard urges him to be strong and resolved in the face of these problems, and to be observed to be unshakable. But John reports that he has made a deal with Pandolf. The Bastard is upset to hear of this alliance and urges the king to fight. John permits the Bastard to take command of his forces.
Louis the Dauphin marches with Salisbury, Pembroke, Lord Bigot, and the French Count Melun. Louis orders the agreement with the English lords to be written down for posterity. Salisbury assures Louis that they won't break with him, despite the strange fact that he and other sons of England have come to march with England's enemy. He pauses to weep for his nation and wishes he could escape having to witness two armies combine on its soil. Louis compliments Salisbury on his noble sentiments and urges him onward to a successful fight.
Pandolf enters, announces that John has reconciled with Rome, and orders Louis to withdraw his army. Louis refuses, saying he is too high-born to be ordered about or used as a tool by any other power. Pandolf urged on the war, he says, but now it is too big to be smothered. He evokes Arthur, reminding Pandolf that he takes up Arthur's claim to the throne, and won't back down just because John has made peace with Rome. He's not Rome's slave, he insists.
The Bastard enters and asks to speak to Louis. Speaking for John, the Bastard declares that John has prepared an army that will thoroughly destroy France's tiny force, and he tells the English nobles that even their wives have joined the English force. Louis calls for the attack, and the Bastard threatens Louis with the death that John's armies shall mete out.
John and Hubert meet on the battlefield. John is distraught at the battle. A messenger enters and reports that Louis's expected reinforcements have been wrecked at sea. Feeling weak, the king departs to meet the Bastard.
Having scorned the power of Rome before, John now submits to its authority in hopes that Pandolf will be able to hold off the invaders. (Given the religious and political climates of Shakespeare's time, this act is--as the Bastard comprehends--a clear statement of John's uncertainty and weakness; if he was ever an impressive or powerful figure, he is now suffering a quick decline.) Like John's effort to win back his nobles by reporting that Arthur was not murdered, this ploy comes too late to have the desired result. Louis too resists the authority of Rome now that he is so close to gaining the throne and continues his attack.
The Bastard demonstrates an extraordinary ability to bluff when he threatens Louis, insisting that John's army is so enormous that it will completely annihilate Louis' forces. He describes the destruction that will be wrought; but Louis is shrewd enough not to believe him. Unfortunately for Louis, he should listen to the Bastard: While it is true that John's army is not as large as the Bastard claims, Louis's forces will soon be shipwrecked--yet again--and decimated at sea.