King John enters holding the hand of King Philip. Louis and Blanche follow, then Eleanor, the Bastard, and Austria. Philip announces that the great day of the wedding will become an annual festival. Constance appears to contradict Philip, cursing the unfortunate and unlucky day when Philip let his family be joined with John's instead of Arthur's. Philip tries to calm her, but she accuses him of having treated her falsely; he swore to join her in defeating John's army, but now he has merged with John. Austria too tries to soothe her, but she curses him for having gone over to the other side.
Cardinal Pandolf enters, arriving to speak on behalf of the Catholic pope. He turns to John and demands to know why he has barred the pope's chosen nominee from becoming the Archbishop of Canterbury. John replies that no Italian priest will tell him what to do in his kingdom, for he has the divine right to rule as he sees fit. Philip warns him against defying the church, but John rails against the meddling and corrupt powers of the Catholic Church. Pandolf announces that he will excommunicate John, and will celebrate any who go against John.
Constance is delighted and asks Pandolf to support her curses against John. Pandolf says his curses, unlike hers, are lawful; but she declares that if the law can't give her child the throne because John controls the law, then law is inadequate and cannot stop her from cursing John. Pandolf calls for Philip to let go of John's hand and set his forces against John's. Constance, Eleanor, the Bastard, and Austria all urge Philip with conflicting suggestions. Louis says that it is worse to break with Rome than to lose a friend in England. Philip remains silent throughout the discussion, revealing only that he is perplexed.
Pandolf threatens to also excommunicate Philip, but Philip asks Pandolf to put himself in Philip's place. Imagine, he says, that you've just joined the King of England in marriage, a legal tie of peace and love between the kingdoms. Should he destroy this new peace? He asks Pandolf to suggest another way. Pandolf urges him again to be the church's champion, and break with England. Philip says he will let go of John's hand, but he won't forgo his faith in their bond. Pandolf declares he thus sets his faith in John against his faith in the church. It is not immoral, he says, to break an immoral oath with England. He reminds Philip that his primary oath was to the church and asks him to honor his earlier oath by breaking his later allegiances to John.
Blanche cries out against Pandolf, insisting that her wedding day not be marred with war and slaughtered men. She begs her new husband to hear her and not to go to battle against her Uncle John. Constance begs Louis to go ahead with the destruction of England, now apparently called for by the powers of fate. Philip remains silent, so Pandolf announces that he will curse him. But Philip finally relents, and he drops John's hand. John and his party assure Philip that he will regret his decision, while Blanche mournfully wonders whom she should side with, being now tied to both sides of the new conflict. Philip and John threaten each other and depart to prepare for battle.
The battle breaks out. The Bastard emerges from the fray holding Austria's head. John enters with a captive Arthur, and he asks Hubert to look after him; he leaves to check on the safety of his mother.