Act 4 consists of one long scene of 334 lines. Although we are told at the end of Act 3 that Richard and Bolingbroke will meet in London, at first we do not get that meeting. Instead it’s a scene in which Bolingbroke is present, and presumably presiding, when Bagot accuses York’s son Aumerle of persuading Richard to approve the murder of Gloucester, and then of carrying it out. Aumerle denies it, and Fitzwater, Percy, and an unnamed “Lord” take Bagot’s side while Surrey takes Aumerle’s. And the banished Norfolk is reported to have said that Aumerle is guilty. As Richard did in Act 1, Bolingbroke, acting a king-like role, judiciously declares there will be a trial — when Norfolk returns. This has the effect of postponing the trial. And it makes Bolingbroke look good, since he does not rush to judgment (as he did with Bushy and Green).
This sets up the big scene between Richard and Bolingbroke. It’s notable that before Richard comes in, we get a report from York that Richard “with willing soul/ Adopts [Bolingbroke] heir, and his high sceptre yields/ To the possession of thy royal hand.” Shakespeare is here apparently simplifying Holinshed, who had said that Richard “renounced and voluntarilie was deposed” — there’s a paradox there: if it’s voluntary, then presumably you say he “resigned” or “abdicated.” York has consistently respected Richard’s royal status, but he also sides with Bolingbroke, and he apparently wants to avoid saying anything about the king being deposed. But he does say that Richard is “plume-pluck’d,” as if his royal plume was seized by Bolingbroke. And is it possible that this is just another rumor, which may prove to be false (as two earlier rumors were)?
Then comes Carlisle’s renewed defense of Richard as God’s anointed, whereupon he is accused of treason by Northumberland, who arrests him. But on whose authority does he act, his own or Bolingbroke’s? Bolingbroke then refers to “our arrest,” suggesting that, already using the royal we, it was his authority. Maybe he deliberately fudges, and says that it is the joint authority of himself and Northumberland.
I’m not sure why we get the report of the resignation/deposing and then get it again when Richard comes on stage. Maybe, as you suggest, it was because Shakespeare knew that the on-stage resignation might be censored, and he needed to include reference to Richard’s yielding. In any case, this time we get an ambiguous resignation (as in Holinshed). Richard literally “resigns” and “gives” the crown to Bolingbroke, in a theatrically stunning moment, then declines to answer whether or not he is “contented” to do so, but then formally and even ritually “gives.” But he says he retains the “cares” of a monarch. His emphasis on “care” looks ahead to Henry IV’s “uneasy . . . head.” It also looks back to Richard’s speech about the “sad stories of the death of kings.” In that speech, all kings die, and all suffer want and grief. Now in Act 4 he says that it’s not just reigning kings: deposed kings do not escape care or grief.
Again Northumberland plays the heavy by demanding that Richard confess to crimes. By what authority does he do this? Maybe again by prior agreement with Bolingbroke, but when Richard resists, Bolingbroke eventually tells Northumberland to back off. I suppose this is designed to make him look more reasonable than the vengeful Northumberland.
And then follows the “mirror” scene. It’s not clear to me why Richard calls for a mirror and then “reads” his face in the mirror. This leads to a quite theatrical effect when he breaks the mirror, and symbolically shatters his regal status.
Bolingbroke sends Richard to the Tower, though it’s not clear whether it’s for Richard’s safekeeping (as in Holinshed) or to hold him for punishment. And the final part of the scene serves to postpone any resolution until Act 5: Carlisle and Westminster are plotting some kind of resistance, and that resistance must be overcome before Richard can die and Bolingbroke can ascend the throne.
Act 4 seems to begin with almost comic confusion, charges of lies and counter lies, one gage thrown down in response to another. Bolingbroke forbids Bagot from picking up Aumerle’s, but then Fitzwater throws down his, then Percy on Fitzwater’s side, then “another lord,” then Aumerle asks if anyone can lend him a gage to challenge Norfolk, who is I think Mowbray. But that’s futile, as the bishop of Carlisle reports that Norfolk/Mowbray is dead and describes him in holy and heroic terms as a crusader. Even his old foe Bolingbroke blesses him and wishes his soul to the bosom of “good old Abraham.” So all these confusing challenges will rest “under gage” in Bolingbroke’s charge. Why Bolingbroke? As if to answer, York comes in with the news that Richard is willing to abdicate and adopt Bolingbroke as his heir. (Was John of Gaunt the next brother in line for the throne after Edward, Prince of Wales? No, but Gaunt was the only royal uncle with a male heir, I think.) Carlisle objects and makes the case for the illegality of Richard’s deposition and predicts the Wars of the Roses. Northumberland plays the heavy, as he always seems to do, and arrests Carlisle, whose position as a clergyman seems to protect him from execution.
When Bolingbroke orders Richard brought it, Richard appears to become a more sympathetic character than he has previously, as he seems to garner more sympathy in defeat. And he also appears a more effective enacter of royalty that he was as king. I imagine him holding out the crown to Bolingbroke as if to give it to him, then as the latter puts his hand on it, drawing it back and saying, “Here, cousin, seize the crown,” as if to create a visual image of what’s taking place. Bolingbroke is reduced to a somewhat lame, “I thought you had been willing to resign.” As you say, it’s theatrically stunning. As Richard renounces all the elements of his kingship, the poignancy of his human loss emerges. And his demonstration with the looking glass continues this. And Northumberland continues his role as political heavy. And the short exchange between Aumerle, the abbot, and Carlisle, lets us know it’s not entirely over.