At court, Mortimer Junior rejoices in the execution of Edward's supporters as well as at the imprisonment of the “light-brained King.” He urges Isabella to “be ruled by [him]” and arrange for Prince Edward's coronation: he himself will then act as Protector. Isabella agrees that Mortimer can do anything he likes to Edward II as long as her son is safe.
Given Mortimer's previous objections to Gaveston's influence over Edward, his determination to control both Isabella and Prince Edward is deeply hypocritical. Although Mortimer is a noble by birth, he would not be able to wield the kind of power he now enjoys if he were not having an affair with Isabella. Mortimer and Isabella's relationship therefore ends up being just as destructive to the normal social hierarchy as Edward's relationship with Gaveston.
A messenger arrives from Kenilworth, followed shortly afterward by the Bishop of Winchester. Isabella feigns distress at the news of Edward's unhappiness, but sends for Prince Edward when she sees the king's crown. The Bishop further explains that it’s been discovered that Kent is plotting to help his brother escape, and that Edward has been put in Berkeley's custody. He warns, however, that Berkeley may pity the King too much to be trustworthy. Mortimer Junior consequently plans to move Edward, but Isabella hints that it might be safer to simply kill him.
Although Mortimer believes he fully controls Isabella, her interactions with him in this scene suggest that that may not be the case. The idea to kill Edward is Isabella's, but she manages to sidestep direct culpability for it: when Mortimer urges her to say directly whether Edward should be murdered, she hedges, saying that she wishes he were dead but not by her "means." Isabella, in other words, understands the power her speech has to harm her. This is not the case with Mortimer, whose guilt is ultimately discovered by means of a written message.
Mortimer Junior summons Gourney and Maltravers, entrusting the latter with a message dismissing Berkeley. He then gives Gourney detailed instructions on how to deal with Edward, telling him not only to move him from place to place to thwart Kent's plans, but also to “amplify [Edward’s] grief with bitter words.” If Gourney complies with these orders, Mortimer says, he will “rise” alongside Mortimer himself, “who now makes Fortune's wheel turn as he please.” Gourney then prepares to leave, but before he does so, Isabella gives him a jewel to give to Edward as evidence of her love.
Mortimer's belief that he can conquer chance and dictate his own fate is the clearest example yet of the kind of hubris that often characterizes tragic heroes. Mortimer, however, lacks the larger-than-life presence of a typical tragic hero, mainly because he shares a play with so many other tragic characters (most notably Gaveston and Edward II). This ultimately underscores Marlowe's usage of Fortune's Wheel, however: all the characters in the play who wield power end up reduced to the same status, even in terms of the amount of "screen time" they receive.
Gourney leaves, and Mortimer Junior tells Isabella in an aside to keep up her pretense: Prince Edward and Kent have just walked in the room. The two of them continue to speak to one another privately, speculating that Kent is attempting to gain control of the Prince. Aloud, Mortimer and Isabella exchange greetings and commiserations with Kent, who nevertheless realizes that they are lying.
Isabella and Mortimer's distrust of Kent speaks to the dishonesty of their motivations. As Mortimer himself points out, Kent's relationship to Prince Edward would make him a natural candidate for the Protectorship—certainly more natural than Mortimer, who is not closely related to the Prince. Clearly, however, Mortimer is now more concerned with wielding power than with maintaining the established social hierarchy.
The conversation turns to Prince Edward and the Protectorship: Kent denies aspiring to the position, while the Prince himself begs not to be crowned king on the grounds that he is too young. He then relents, but only if he can see Edward II and learn what his father wants to have happen. Isabella, however, says that this is impossible, and she, Mortimer Junior, and Kent begin to argue: Kent doubts the couple's sincerity, and Mortimer Junior claims to fear to allow Kent—who “hath betrayed the King, his brother”—near the Prince. Prince Edward then joins the argument on Kent's side, prompting Mortimer to drag the prince out of the room by force. Now alone with Isabella, Kent demands the return of the Prince. Isabella refuses, so Kent departs to try to rescue his brother from Kenilworth.
In this passage, Mortimer is able to use the importance of family ties in order to discredit Kent. Although both Mortimer and Kent have rebelled against their monarch, only Kent has committed the "crime" of rebelling against his own flesh and blood. The implication is that only someone truly depraved would act in such an unnatural way, and that Kent therefore cannot be trusted around the Prince. Of course, the fact that Mortimer ignores Prince Edward's own wishes and then pulls him from the room reveals that he does not have the Prince's best wishes at heart either.